CA1084183A - Branched path, path routing arrangement and systems - Google Patents
Branched path, path routing arrangement and systemsInfo
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- CA1084183A CA1084183A CA261,634A CA261634A CA1084183A CA 1084183 A CA1084183 A CA 1084183A CA 261634 A CA261634 A CA 261634A CA 1084183 A CA1084183 A CA 1084183A
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Abstract
BRANCHED PATH, PATH ROUTING
ARRANGEMENT AND SYSTEMS
ABSTRACT OF THE DISCLOSURE
Branched path, path routing arrangements and systems to perform path routing operations for R. F. communication signals between communication terminals is disclosed.
ARRANGEMENT AND SYSTEMS
ABSTRACT OF THE DISCLOSURE
Branched path, path routing arrangements and systems to perform path routing operations for R. F. communication signals between communication terminals is disclosed.
Description
` :
1~84183 This invention relates to communications and more particularly to path routing arrangements and systems for interconnecting audio and/or video electrical intelligence within electrical messag2 envelopes in an R. F. communication system.
.. . .. .
Many common switching systems fall into a ~ -~
category geherally referred to as switched-path, path routing systems. Such systems include manual switched-path, path routing systems, progressive controlled switched-path, path routing systems and common controlled ~
switched-path, path routing systems, all of which are ~ ;?
known in the art. Commonly, today's telephone switching systems use either dedicated (Strowger type)-path or common control switching principles (panel, crossbar, electronic switches) to interconnect subscriber terminals.
In existing systems substantially designed for audio communication, but which are adapted for picture phone transmission, separate paths are commonly used for the audio and video components of the communication signals.
Such adaptation is difficult and the cost may be prohibitive, thus substantially precluding the mass use of picture phone and wideband carrier facilities.
In recent years, primarily because faster routing speeds can be achieved whe~e there is no physical switching, the tendency in modern communication system design has been away from switched-path routing to what is commonly referred to as time division switching or time division multiplexing.
1~84183 This invention relates to communications and more particularly to path routing arrangements and systems for interconnecting audio and/or video electrical intelligence within electrical messag2 envelopes in an R. F. communication system.
.. . .. .
Many common switching systems fall into a ~ -~
category geherally referred to as switched-path, path routing systems. Such systems include manual switched-path, path routing systems, progressive controlled switched-path, path routing systems and common controlled ~
switched-path, path routing systems, all of which are ~ ;?
known in the art. Commonly, today's telephone switching systems use either dedicated (Strowger type)-path or common control switching principles (panel, crossbar, electronic switches) to interconnect subscriber terminals.
In existing systems substantially designed for audio communication, but which are adapted for picture phone transmission, separate paths are commonly used for the audio and video components of the communication signals.
Such adaptation is difficult and the cost may be prohibitive, thus substantially precluding the mass use of picture phone and wideband carrier facilities.
In recent years, primarily because faster routing speeds can be achieved whe~e there is no physical switching, the tendency in modern communication system design has been away from switched-path routing to what is commonly referred to as time division switching or time division multiplexing.
- 2 - ~
1~84183 The technology of time division switching has been used, for example, in relation to carrier telephone transmission, computer technology, and small voice-band private exchanges.
However, as is well known, the performance of time division switching systems is dependent on the synchronization of sampling gates and on sampling rate. As the component frequencies of the communication intelligence increases, the required sampling rate to ensure reproduction of a reasonable facsimile of the intelligence at a receiving terminal increases. Where the same physical path is used for several communication signals appearing in different sample time slots, the sampling rates must further increase.
If the sampling operations are not carefully controlled, the intelligence in a given transmission may be lost or confused with intelligence in another transmission.
It is common to find communication systems which incorporate frequency division between R.F. communication channels to enable two or more communication signals to be transmitted simultaneously over a shared transmission path.
For example, a channel "X" carried on a 50 MHZ (megahertz) carrier frequency may be assigned a frequency band from 50 MHZ to 59 MHZ, and, a channel "Y" carried on a 60 MHZ carrier frequency may be assigned a frequency band from 60 MHZ to 69 MHZ. The two channels can be said to be "divided" in frequency by 10 MHZ (the term "divided" or "division" herein being with reference to the separation in frequency between carrier frequencies). The channels may be transmitted simultaneously over the same ~ransmission path substantially without interference with each other. Often, this is referred to as frequency division multiplexing.
i~84183 It is to be understood herein that when it is said that communication channels or carrier frequencies are divided in frequency from other communication channels or carrier fre~uencies, the amount of separation between carrier frequencies is sufficient to avoid overlap in the frequency bands associated with separate channels or carriers.
If a frequency division multiplexed system comprises a large number of receiving and transmitting terminals, or receiver/transmitter terminals acting as receiver and transmitters at the same time, then a large number of R.F.
communication channels of different frequency will be required if all or several of the terminals are to be active at the same time, sharing the same transmission path.
For example, in a 10,000 terminal communication system, there would be required 10,000 channels divided in frequency from each other to allow 5000 pairs of receiver/transmitter terminals of the system to communicate simultaneously between pairs while sharing the same transmission path.
If the channels were divided in frequency by 10 MHZ (ie.
a 10 MHZ separation between the carrier frequency of a given channel and the carrier frequency of the channels occupying adjacent frequency bands), then the total system bandwidth would be in the range of several gigahertz (of the order of 100 GHZ).
A principal object of the present invention is to provide a new and improved path routing arrangement which is particularly adapted for performing path routing operations for R.F. communication signals.
A further object of the present invention is to provide a new and improved system for interconnecting a large number of R.F. communication terminals wherein the number of R.F. communica-ti.on channels of diEferent frequency associated with the various terminals may be relatively small.
In accordance with the present invention, there is provided a path routing arrangement for interconnecting a plurality of R.F. communication terminals so that a trans-mission path may be established be-tween a desired pair of the terminals. The path routing arrangement comprises a plurality of electrically unbalanced and substantially non-interfering R.F. transmission lines, conduits or the like (herein referred to as "transmission tracks"), which r~
transmission tracks are interconnected by mechanical, electromechanical, or electrical (e.g. semiconductor or diode) gates, which gates are normally closed to prevent R.F. communication signals from passing between transmission tracks interconnected by the gates, but which open in .
response to control input signals to the gates (herein, such gates are referred to as "transmission gates"). The transmission tracks are non-interfering in the sense that when a particular transmission track is carrying an R.F.
communication signal, it does not behave so as to cause electrical interference with co~munication signals being carried by other transmission tracks. The transmission tracks are interconnected by the transmission gates in a "branched path" manner which indicates that various optional paths branch off from the various tracks. More formally, the arrangement can be thought of in the following terms:
The pa-th rou-ting arrangement com.prises pluralities of each - of first, second and third transmission tracks. The plurality of first transmission tracks comprises a plurality of groups of first transmission tracks, and similarly, the plurality of second transmission tracks comprises a plurality of groups of second transmission tracks. For each pair of groups consisting of one of the groups of first transmission tracks and one of the groups of second transmission tracks, a unique one of the third transmission tracks is interconnected by ;~
transmission gates with every first transmission track in the group of first transmission tracks and with every second transmission track in the group of second transmission tracks. -The third transmission tracks are thus said to define branching paths between the first transmission tracks and the second transmission tracks. The path routing arrangement being so structured, a transmission path for R.F. communica-tion signals between any desired first transmission track and any desired second transmission track may be established via the unique third transmission track forming the branching path between the two desired tracks by opening the trans-mission gate interconnecting the desired first transmission track and the particular third transmission track and the transmission gate interconnecting the desired second transmission track and the particular third transmission track.
A transmission path having been so established, communication can take place between an R.F. communication terminal connected to the desired first transmission track and an R.F. communication terminal connected to the desired second transmission track. Where the communication terminals are R.F. receiver/transmitter terminals, such communication may be simultaneous bi-directional transmission, one of the two terminals transmitting on an R.F. carrier frequency which is divided in frequency from an R.F. carrier frequency . , .. . ...... ...... ,.. . ... , . . .,,, ,. . ~
on which the other terminal transmits. At the same time as such communication is taking place, communication may ; also take place between other desired pairs of communication terminals and in this regard there are two situations which may arise.
The first situation is that in which the branching path of the transmission path between one pair of terminals is separate from the branching path of the transmission path between another pair of terminals. In this situation, no portion of the transmission path between one pair of terminals is in common with the transmission path between the other pair of terminals. Owing to the substantially non-interfering characteristic of the transmission tracks generally, it will be readily apparent that communication between one pair of terminals may occupy the same or an ~-overlapping frequency band or bands as communication taking place between the other pair of terminals. Or, of course, the frequency bands may be completely different.
The second situation is that in which a portion of ~ ;
the branching path between one pair of terminals is in common with the branching path of the transmission path -between another pair of terminals. In this regard, it will be appreciated that the unique third transmission track which defines the branching path between any given "group"
(as the term is herein defined) of first transmission tracks and any given "group" of second transmission tracks is effectively common to all transmission tracks in both groups.
Thus, if one terminal of each pair of terminals is connected to separate first transmission tracks of the same group of first transmission tracks, and if the other terminal of each pair of terminals is connected to separate second transmisslon 1~84~33 tracks of the same group of second transmission tracks, then some portion of the transmission path between one pair of terminals is necessarily shared in common with some portion of the transmission path between the other pair of terminals. In this situation, communication may take place between each pair of terminals at the same time provided there is an appropriate selection of the carrier transmission frequencies associated with each terminal. For simultaneous bi-directional transmission between each pair of terminals at the same time, four separate carrier frequencies would be required. It will readily be apparent that additional pairs of terminals could communicate with each other at the same time sharing, in part, the same transmission path by the use of still further carrier frequencies appropriately divided in frequency from all other carrier frequencies.
However, it is to be understood that applications are envisaged where communication between more than one pair of terminals at the same time which would require the sharing of a portion of the same transmission path would not be permitted. ~ere it is contemplated that while a particular third transmission track is occupied (that is, once a transmission path has been established via the particular third transmission track between a given pair of terminals), then no other pair of terminals would be allowed to communicate using the particular third transmission track so long as it remained occupied. The result may be to prevent a desired transmission path from being established at a desired time ("blockage"). It must be remembered that in the case of reference to "blockage", this refers to equipment or route access only and not to busy or "don't answer"
1~84183 conditions at the called terminal. However, it is contemplated, particularly for relatively larse systems where communication takes place essentially between random pair of terminals at random times, that such blockage will be considered to be ~ -of only minor consequence.
Generally, it is contemplated that path routing arrangements in accordance with the present invention will be (though this is not necessary) characterized by a repetitiveness of structure. In this regard, it is contem-plated that the arrangement may comprise "gl" groups of first transmission tracks, each of which groups includes "tl" ~
first transmission tracks, and "g2" groups of second trans- ~ -mission tracks, each of which groups includes "t2" second transmission tracks, where "gl" and "g2" are each integer ;~
numbers greater than 1 and "tl" and "t2" are each integer .:
\
... _ .. ..
_ g _ ~84183 , numbers equal to or greater than 1. Thus, there are then ; "glxtl" first transmission tracks and "g2xt2" second transmission tracks. It may readily be determined that there will be "glxg2" third transmission tracks defining the branching paths between the "gl" groups of first transmission tracks and the "g2" groups of second transmission tracks. Also, it may readily be determined that a path routing arrangement so structured will have "glg2(tl + t2)"
transmission gates to allow a transmission path to be established between any desired one of the "glxtl" first transmission tracks and any desired one of the "g2xt2"
second transmission tracks. Such transmission path would be via the unique one of the "glxg2" third transmission tracks which interconnects the particular group of first transmission tracks of which group the desired first trans-mission track is a member, and the particular group of second transmission tracks of which group the desired second trans-mission track is a member.
In certain embodiments of the present invention, it is contemplated that the aforementioned integer numbers "gl", "g2", "tl", and "t2" will all be identical, say the integer number "n" ("n" being greater than 1). There will then be "n " first transmission tracks (i.e. "n" groups of "n" first transmission tracks), "n " second transmission tracks (i.e.
"n" groups of "n" second transmission tracks), "n " third transmission tracks, and "2n " transmission gates. Herein, a path routing arrangement so structured is characterized as being "symmetric". It is contemplated that such embodiments will be particularly suitable for a commu~ication system interconnecting "n2" subscriber communication terminals, 1(~8418;~
each subscriber cerminal beiny an R.F. communication -receiver/transmitter terminal connected to a unique one of the first transmission tracks of the path routing arrangement and to a unique one of the second transmission tracks of the path routing arrangement. According to this embodiment, any one of the subscriber terminals may communicate with any other one of the subscriber terminals.
It is contemplated that the connection between each i~
of such subscriber terminals and the transmission tracks may ~-include line equipment means having a calling mode of opera-tion and a called mode of operation, the terminal which initiates a call being referred to as the calling terminal and the terminal receiving the call being referred to as the called terminal. In the calling mode of operation, the line equipment means is for receiving R.F . communication signals as an input from the subscriber terminal and providing such communication signals as an input to the first transmission ;~
track to which the subscriber terminal is connected, and for receiving R.F. communication signals as an input from such -.~
first transmission track and providing such communication signals as an input to the subscriber terminal. In the called mode of operation, the line equipment means is for receiving R.F. communication signals as an input from the subscriber terminal and providing such communication signals as an input to the second transmission track to which the terminal is connected, and for receiving R.F. communication signals as an input from such second transmission track and providing such communication signals as an input to the subscriber terminal. ~hen communication takes place between a pair of terminals, one terminal would be in the calling 1~8418;~
mode of operation and the other terminal would be in the called mode of operation. The transmission path between the terminals can be considered as consisting of three portions: Vi2. a first portion between the calling terminal and its line equipment means, a second portion between the line equipment means of the calling terminal and the line equipment means of the called terminal, and a third portion between the line equipment means of the called terminal and the called terminal. The second portion of course comprises the transmission path through the path routing arrangement.
In one embodiment of the present invention, it is contemplated that the line equipment means of the terminals will include carrier frequency translation means for trans-lating the carrier frequency of R.F. communication signals ~-received as an input by the line equipment means. As will become more apparent hereinafter, the purpose of translating the carrier frequency is to produce a desired division between the carrier frequency of one R.F. communication signal and the carrier frequency of another R.F. communication signal, both of which signals are being transmitted at the same time over the previously mentioned first, second and third portions of the transmission path between the pair of terminals. For example, it is contemplated that in certain embodiments of the present invention, the system will comprise a plurality of subscriber communication terminals interconnected by the path routing arrangement so that bi~directional simultaneous transmission may take place between terminals.
According to such embodiments, it is contemplated that each terminal will be adapted to transmit on a predefined carrier frequency ana adapted to receive on a preclefined carrier frequency, the transmitting carrier frequency being divided in frequency from the receiving carrier frequency by a predetermined amount so that the transmitting and receiving frequency bands do not overlap. It is further contemplated that the predefined transmitting carrier ;~
frequency of any given terminal may be one of a relatively ;
- few (e.g. 10) possible transmitting carrier frequencies, -and not necessarily different than the transmitting carrier frequencies of all other terminals. Similarly, it is contemplated that the predefined receiving carrier frequency of any given terminal may be one of a relatively few (e.g. 10) possible receiving carrier frequencies, different than all of the possible transmitting carrier frequencies but not necessarily different than the receiving carrier frequency of all other terminals. In such cases, one way of maintaining a division of frequencies between communicating subscriber terminals is to include frequency translation means in the line equipment means of the terminals. Such frequency translation means may be operative as follows: (a) in the calling mode of operation: (i) to translate, if necessary, the carrier frequency of communication signals received as ;
an input from the second portion of the transmission path to the receiving carrier frequency of the calling terminal (which signals are then provided as an input to the calling terminal via the first portion of the transmission path), and, (ii) to provide as an input to the second portion of the transmission path, communication signals received from the calling terminal via the first portion of the transmission path (i.e. without frequency translation); and, (b) in the called mode of operation: (i) to translate the carrier frequency of communication signals received as an input from the second portion of the transmission path to the receiving carrier frequency of the called terminal (which signals are then provided as an input to the called terminal via the third portion of the transmission path), and, (ii) to translate the carrier frequency of communication signals received from the called terminal via the third portion of the transmission path to the receiving carrier frequency of the called terminal (which signals are then provided as an input to the second portion of the trans-mission path). Such provision for carrier frequency translation will maintain a division of frequency between carrier frequencies along the respective first, second, and third portions of the transmission path between the terminals, and at the same time will ensure that the communi-cation signals received by each terminal are on the carrier frequency which each terminal is adapted to receive. As will be appreciated by those skilled in the art, and as is discussed in more detail hereinafter, there are several ways other than the foregoing example whereby frequency translation means may be incorporated into the lines equipment means of a system for the purpose of maintaining a desired division of carrier frequencies over various portions of a transmission path between communication terminals Transmission tracks used in a path routing arrangement in accordance with the present invention are, as hereinbefore stated by definition, electrically unbalanced and substantially non-interfering R.~. transmission lines, conduits or the like.
The use of such transmission tracks permits the use of a branched path, path routing arrangement as an R.F. communication 1084~L83 routing device. Coaxial lines are an exemplary Eorm Of such transmission lines. They are unbalanced and the outer conductor of such lines provides a shielding effect and thereby contains R.F. communication signals so that that when such signals ;
are being transmi-tted on the line they will no~ substantially interfere with R.F. communication signals that are being transmitted on other lines which may be closely adjacent.
However, as will be apparent to those skilled in the art, the transmission tracks may have a structure other than -that of coaxial lines. For example, waveguides may be -`
used for transmission at microwave frequencies. (As a matter of economy, it is contemplated that waveguides would not be used unless the bandwidth requirements of the communication signals otherwise dictated.) The transmission gates of a path routing arrangement in accoxdance with the present invention may, as stated hereinbefore, be mechanical, electromechanical, or electrical (e.g. semiconductor or aiode) gates~ In one embodiment of the present invention, it is contemplated that such gates will be identified by a designated code and will include means for receiving a coded input signal, and, if the coded input signal received represents, in a selected code, the identification of the gate, for causing ~he gate to open and allow R.F. communication signals to pass bétween the transmission tracks interconnected by the gate. In a particular species of this embodiment, it is contemplated that a transmission gate will include means for detecting the coded input signal when such signal is applied as an input to a transmission track to which the gate connec_s. Such coded input signal may, for example, be provided to a ~ - 14a -1~84183 transmission track as modulated or unmodula-ted carrier signals having a frequency sufficiently high to propagate in the transmission track.
Of course, coded input signals to control trans-mission gates may be provided on control signal lines separate from the transmission tracks. Here r such control signals may, for example, be provided in digital form.
For example, the transmission gates may be identified by a binary-coded-decimal code, and the coded signals to control the gates provided in parallel or sequential order as inputs to the control signal lines which lead -to the gates. The implementation of such means for controlling transmission gates will be readily apparent to those skilled in the art.
Where the path routing arrangement is relatively small such as may be used in an inter-office communication system, it is conceivable that situations could arise where it may be desired to use manually operated mechanical transmission gates, e.g. a switch for making or breaking an electrical connection between transmission lines.
Branched path structures are, in a general sense, not new. In this regard, U. S. Patent No. 3,699,295 (Shinohara et al) which issued on October 17, 1972, may be of some interest in relation to the present invention.-This patent indicates that branched path structures per se are old and goes on to describe a particular arrangement for a branched path structure.
However, an important distinction is to be made between known branched path structures such as those disclosed or discussed in the Shinohara patent and branched ~ - 14b -1~84183 path structures in accordance with the present invention.
In contrast to the present invention, the transmission paths in the prior art structures are electrically balanced and are not particularly adapted for R. F. operation, and teach space divided, in contrast to frequency divided transmission paths for bi-directional operation (full duplex). Such transmission paths do not comprise "transmission tracks" as the term is herein defined. As a result of using electrically unbalanced, frequency divided, and substantially non-interfering R. F. transmission lines, conduits or the like, the present invention requires only one transmission gate at each branching point of the branched path structure and two gates for all terminal to terminal calls. Electrically balanced, branched path structures teach two gates or switches at each branching point and eight gates or switches for terminal to terminal calls.
The concept of performing, in a branched path, path routing arrangement (which may occupy a relatively small physical space), path routing operations for R. F.
communication signals being transmitted between pluralities of R. F. communication terminals (many of which terminals may be transmitting on the same carrier frequency), appears to be alien to the prior art. In addition, there appears to be no teaching in the prior art of the use of frequency division multiplexing in a branched path, path routing system. As will become more apparent hereinafter, for systems wherein a large number of communication terminals are interconnected, the combination of frequency division multiplexing and branched path routing permits a significant reduction in the number of R. F. communication channels of different frequency reasonably required to allow communications to take place between pluralities of desired pairs of the terminals at the same time.
\~
~ - 14c -1~84~83 The foregoing and other features of the present invention will now be described with reference to the drawings in which:
FIGURE 1 is a perspective view symbolically illustrating a portion of a branched path, path routing arrangement which may be used in a system inter-connecting 10,000 R.F. subscriber terminals.
FIGURE 2(a) symbolically illustrates one transmission path through the path routing arrangement of FIGURE 1.
].0 FIGURE 2(b) illustrates an alternate arrangement for one transmission path through a path routing arrangement generally similar to the path routing arrangement shown in FIGURE 1.
FIGURE 3 illustrates a typical interconnection between a portion of a cross horizontal transmission track of FIGURE 1 and back and front horizontal transmission tracks of FIGURE 1.
. FIGURE 4 illustrates a typical interconnection between a portion of a vertical transmission track of FIGURE 1 and front horizontal transmission tracks of FIGURE 1. ~-FIGURE 5 is a circuit diagram of a transmission gate which responds to input signals coded by audio tones and which signals are provided as an input to a :
transmission track.
FIGURE 5(a) illustrates a modification to the circuit of FIGURE 5 whereby the coded input signal is required to include additional audio tones to operate the transmission gate.
FIGURE 6 illustrates typical waveforms at various points during the operation of the circuit of FIGURE 5.
~ - 14d -~084183 FIGURE 7 is a portion of a circuit diagram of a simplified transmission gate.
FIGURE 8 illustrates a portion of a system incorporating the path routing arrangement of FIGURE 1 and interconnecting a plurality of audio/video subscriber terminals.
FIGURE 8(a) illustrates a variety of possible carrier frequency assignments along various portions of a bi-directional transmission path between a calling subscriber ter-minal and a called subscriber terminal.
FIGURE 9 is a circuit diagram of line equipment associated wlth a subscriber terminal in the system of FIGURE 8.
FIGURE 10 is a detailed circuit diagram of the calling control circuit of FIGURE 9.
FIGURE 11 is a detailed circuit diagram of the called control circuit of FIGURE 9.
FIGURE 12 is a circuit diagram of a circuit to automatically tune the frequency of a receiver to receive a desired frequency channel. , FIGURE 13(a) illustrates a modification to the circuit of FIGURE 9 to enable a calling party to identify itself to a called party.
FIGURE 13(b) illustrates a modification to the circuit of FIGURE 9 to enable a called party to receive a tone that identifies a calling party.
FIGURE 14 illustrates a conventional resistive hybrid circuit for the circuits of FIGURES 9 and 13(a).
FIGURE 15 is a circuit diagram of a diode transmission gate interconnecting two transmission tracks.
.
~ - 14e -1~84183 DETAILED DESCRIPTION
The detailed description which follows is primarily confined to a relatively large and symmetric branched path, path routing arrangement which may typically be used to interconnect a plurality of R.F. communication terminals so that communication links may be established via transmission paths defined through the arrangement between desired pairs of terminals. The path routing arrangement per se is - described in terms which contemplate the use of the arrangement in a subscriber communication system wherein simultaneous bi directional communication is to take place between pairs of subscriber terminals - one terminal of a pair being the terminal of a calling party, and the other terminal of a pair being the terminal of a called party. This description is then followed by a description of systems incorporating the path routing arrangement.
Referring now to the drawings, FIGURE l shows an illustrative embodiment, in simplified form, of a symmetric branched path, path routing arrangement l for providing bi-directional communication links via transmission paths defined through the arrangement between a plurality of ;-incoming lines and a plurality of outgoing lines. The communication links that are established will be between desired ones of the incoming lines (for example, line I
or line I9902) and desired ones of-the outgoing lines (for example, line 09901 or line 09997). An incoming line may be thought of as being associated with a calling party and an outgoing line may be thought of as being associated with a called party.
In the embodiment shown in FIG~RE l, it has been assumed for purposes of illustration that the path routing ~ - 14f - .
10~34183 operations are to be performed between lO,000 incoming bi-directional transmission lines Ioooo, Ioool, ..., Ig999, and lO,000 ou-tgoing bi-directional transmission lines 0000o/
0 0 999 (only lines Iolol~ I9902t 09901 09997 having been shown). The figure 10,000 is somewhat arbitrary but facilitates comparison with conventional lO,000 line switches used in conventional telephone systems. Also, as will become apparent, the selection of lO,000 permits a geometric order for the arrangement based upon the more familiar decimal system of counting.
Between any given incoming line I and any given outgoing line ~, a unique and self-contained transmission path may be established. Each such path includes a vertical trans-mission path V (e.g. Vl l)' a front horizontal transmission track F (e.g. Fl 99), a cross horizontal transmission track C
(e.g. Cg9 99), and a back horizontal transmission track B (e.g.
B99 99). Each such path also includes two transmission gates, namely, a "vertical" transmission gate GV (e.g. GVl l 99)' which is a transmission gate interconnecting a vertical trans-mission track and a front horizontal transmission track, and a "horizontal" transmission gate GH (e.g. GHl 99 97), which is a transmission gate interconnecting a front horizontal transmission track and a cross horizontal transmission track. In addition, each transmission path also includes a ~'slot" S (e.g. Sg9 99) ~-interconnecting the cross horizontal transmission track of the path and the back horizontal transmission track of the path.
A slot forms a direct electrical connection between the tracks it interconnects so that whenever a communication signal appears on one of the tracks it also appears on the other of the tracks.
Ideally, a slot presents no loss for communication signals.
J~ ' ' ~ - 14g -1~84183 The purpose of the slots is discussed hereinafter - they are not necessary elements of a branched path, path routing arrangement but they may serve to physically govern where transmission lines external to the arrangement (such as transmission line 0 in FIGURE 1) may be conveniently connected to the arrangement.
Thus, for example, the transmission path between line Iolol and line 09997 includes vertical transmission track Vl 1' vertical transmission gate GVl 1 99~ front horizontal transmission track Fl 99, horizontal transmission gate GHl 99 97, cross horizontal transmission track Cg9 97, slot Sg9 97 and back horizontal transmission track Bg9 97.
According to the terminology used in the introductory portion of this specification, a vertical transmission track may be considered as a "first" transmission track, a front horizontal transmission track may be considered as a "third" transmission track, and, a cross horizontal transmission track in combination with a slot and the back horizontal transmission track to which that slot interconnects may be considered as a "second" trans-mission track. In the latter case, for example, the combination of cross horizontal transmission track Cg9 99, back horizontal transmission track Bg9 99, and slot Sg9 99, can be considered as a "second" transmission track in accordance with the earlier terminology.
In general, as can be seen in FIGURE 1, the path routing arrangement comprises a vertical stack 8 of vertical platforms VPp(p=o~99) lying in y-z planes, and a horizontal stack 9 of horizontal platforms HPr (r=0,99) lying in x-z planes. The platforms provide rigidifying support for the transmission tracks and while not considered essential, are ~ - 14h -10~4183 considered desirable to import added mechanical strength and, as will be seen, to facilitate maintenance.
Each vertical platform VPp (p=0,99) includes a plur-ality of vertical transmission tracks Vpq (q=0,99) spaced parallel to each other and extending vertically on the platform (i.e. in the y-direction). Each horizontal platform HPr (r=0,99) includes a plurality of back horizontal transmission tracks Brs (s=0,99), a plurality of cross horizontal transmission tracks Crs (s=0,99), and a plurality of slots Srs (s=0,99).
The cross horizontal transmission tracks Crs are spaced parallel to each other and extend horizontally on the platform (i.e. in the x-direction). For each cross horizontal transmission track Crs, there is one corresponding slot Srs from which extends in the z-direction a corresponding back horizontal transmission track BrS. The slots of differing cross horizontal transmission tracks on the same platform are disposed relative to each other in the x-direction so that the corresponding back horizontal transmission tracks are evenly spaced in the x-direction.
For each pair of platforms consisting of a vertical platform VPp(p=o~99) and a horizontal platform HPr (r=0,99), there is a corresponding front horizontal transmission track Fpr which extends in the z-direction and interconnects with every vertical transmission track Vpq (q=0,'99) of the vertical platform VPp by means of a vertical transmission gate GVpqr (q=0,99) and with every cross horizontal transmission track Crs (s=0,99) of the horizontal platform HPr by means of a horizontal transmission gate GHprS (s=0,99). As can be seen in FIGURE 1, the portions of the front horizontal transmission tracks Epr on a horizontal platform HPr are interspaced with back horizontal transmission tracks BrS on the same platform.
~ - 14i -It should be noted that elemen-ts bearing the generalized subscripts p, q, r, and s are not shown as such in FIGURE 1.
Instead, only three vertical platforms VP0, VPl, and VPg9, and three horizontal platforms HPo, HP98, and HPg9, together with some of the transmission tracks, transmission gates and slots on each platform are shown. However, the basic geometry and overall structure of path routing arrangement 1 should be readily apparent upon consideration of FIGURE 1. Each vertical :~
platform VPp includes 10,000 vertical transmission gates GVpqr (q=0,99; r=0,99) forming a 100x100 matrix of interconnec- -tions between 100 vertical transmission tracks Vpq ~q=0,99) and 100 front horizontal transmission tracks Fpr (r=0,99); and, there are 100 vertical platforms VPp (p=0,99). Similarly, each horizontal platform HPr includes 10,000 horizontal transmission gates GHprS (p=0,99; s=0,99) forming a 100x100 matrix of inter-connections between 100 cross horizontal transmission tracks Crs (s=0,99) and 100 front horizontal transmission tracks Fpr (p=0,99); and, there are 100 horizontal platforms HPr (r=0,99).
On each hbrizontal platform HPr there are 100 slots Srs (s=0,99) forming a diagonal of interconnections between the 100 cross horizontal transmission tracks Crs (s=0,99) and the 100 back horizontal transmission tracks BrS (s=0,99) of the platform.
It will be recognized upon reference to FIGURE 1 that although a complete transmission path through path routing arrangement 1 between a given incoming line I and a given outgoing line ~ is unique, portions of the front horizontal transmission track which is part of such path are necessarily common to other transmission paths through the arrangement. For example, the portion of front horizontal transmission track Fl 99 between vertical transmission gate GVl 99 99 on vertical platform VPl ` ~08418~
and horizontal transmission gate GH1 99 0 on horizontal platform HPg9 is common to every path between vertical transmission tracks ~;~
Vl 0, V~ Vl 99 and cross horizontal transmission tracks Cgg o~ Cgg 1' --~ Cgg 99. ~, FIGURE 2(a) illustrates some additional aspects of the transmission paths of path routing arrangement 1 of FIGURE 1.
Ordinarily, the arrangement 1 will be contained in a rectangular ' enclosure which can be thought of as having a front wall 5 and a ,' back wall 7, each opposed on opposite sides of a stack dividing plane 6, which plane divides the vertical stack 8 from the horizontal stack 9. The vertical stack 8 is between the front :
wall 5 and the stack dividing, plane 6, and the horizontal stack 9 is between the back wall 7 and the stack dividing plane 6. ' ':
By way of example, FIGURE 2(a) shows the transmission path between incoming line Iolol and outgoing line 09997 and includes the specific elements Vl 1' Fl 99, Cg9 97, Bg9 97, GVl 1 99~ GHl 99 97, and Sg9 97 as are shown in FIGURE 1. In addition, the transmission path is now shown to include connectors ..
2, 3 and 4. Connectors 2 and 3 respectively serve the obvious purpose of means for connecting incoming line Iolol and outgoing ~ -line 09997 to the transmission path. Connector 4, which is , included as a part of front horizontal transmission track Fl 99, exemplifies a preference that the portion of a front horizontal transmission track on a vertical platform be separable from the corresponding portion of the front horizontal transmission track ;~
on a horizontal platform. Thereby, an'entire~.platform may~.readily be removed from the stack in which it appears;. This will facilitate maintenance or repair of transmission tracks or ~, :
transmission gates on the platform and will facilitate replace-ment of the platform.
~ - 14k -As is known, undes ~ re ~ ection of communication signals may be produced on an R. F. transmission line if the signals encounter an impedance mismatch. Various techniques for impedance matching are known in the art; the specific choice in any case will probably be governed by empirical considerations.
Such impedance matching devices and techniques are not within the scope of the present invention. In figure 2(a) the provision on respective tranmission tracks of impedance matching loads has been symbolically depicted by load terminations 11.
Each transmission track of path routing arrangement 1 may be coaxial line suitable to concurrently carry several R. F. communication channels, each channel having an associated carrier frequency and a predetermined bandwidth, the carrier frequencies of all channels being divided from each other by a predetermined amount so that the frequency bands of respective channels do not overlap. For purposes of illustration, it will be assumed that path routing arrangement 1 is for use in con-junction with an audio/video communications system wherein a communications signal entering the arrangement from an incoming line I may occupy any one of a first group of ten predetermined "LOW" channels, and wherein a communications signal entering the arrangement from an outgoing line ~ may occupy any one of a second group of ten predetermined "HIGH" channels; as follows:
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~ - 141 -~84183
1~84183 The technology of time division switching has been used, for example, in relation to carrier telephone transmission, computer technology, and small voice-band private exchanges.
However, as is well known, the performance of time division switching systems is dependent on the synchronization of sampling gates and on sampling rate. As the component frequencies of the communication intelligence increases, the required sampling rate to ensure reproduction of a reasonable facsimile of the intelligence at a receiving terminal increases. Where the same physical path is used for several communication signals appearing in different sample time slots, the sampling rates must further increase.
If the sampling operations are not carefully controlled, the intelligence in a given transmission may be lost or confused with intelligence in another transmission.
It is common to find communication systems which incorporate frequency division between R.F. communication channels to enable two or more communication signals to be transmitted simultaneously over a shared transmission path.
For example, a channel "X" carried on a 50 MHZ (megahertz) carrier frequency may be assigned a frequency band from 50 MHZ to 59 MHZ, and, a channel "Y" carried on a 60 MHZ carrier frequency may be assigned a frequency band from 60 MHZ to 69 MHZ. The two channels can be said to be "divided" in frequency by 10 MHZ (the term "divided" or "division" herein being with reference to the separation in frequency between carrier frequencies). The channels may be transmitted simultaneously over the same ~ransmission path substantially without interference with each other. Often, this is referred to as frequency division multiplexing.
i~84183 It is to be understood herein that when it is said that communication channels or carrier frequencies are divided in frequency from other communication channels or carrier fre~uencies, the amount of separation between carrier frequencies is sufficient to avoid overlap in the frequency bands associated with separate channels or carriers.
If a frequency division multiplexed system comprises a large number of receiving and transmitting terminals, or receiver/transmitter terminals acting as receiver and transmitters at the same time, then a large number of R.F.
communication channels of different frequency will be required if all or several of the terminals are to be active at the same time, sharing the same transmission path.
For example, in a 10,000 terminal communication system, there would be required 10,000 channels divided in frequency from each other to allow 5000 pairs of receiver/transmitter terminals of the system to communicate simultaneously between pairs while sharing the same transmission path.
If the channels were divided in frequency by 10 MHZ (ie.
a 10 MHZ separation between the carrier frequency of a given channel and the carrier frequency of the channels occupying adjacent frequency bands), then the total system bandwidth would be in the range of several gigahertz (of the order of 100 GHZ).
A principal object of the present invention is to provide a new and improved path routing arrangement which is particularly adapted for performing path routing operations for R.F. communication signals.
A further object of the present invention is to provide a new and improved system for interconnecting a large number of R.F. communication terminals wherein the number of R.F. communica-ti.on channels of diEferent frequency associated with the various terminals may be relatively small.
In accordance with the present invention, there is provided a path routing arrangement for interconnecting a plurality of R.F. communication terminals so that a trans-mission path may be established be-tween a desired pair of the terminals. The path routing arrangement comprises a plurality of electrically unbalanced and substantially non-interfering R.F. transmission lines, conduits or the like (herein referred to as "transmission tracks"), which r~
transmission tracks are interconnected by mechanical, electromechanical, or electrical (e.g. semiconductor or diode) gates, which gates are normally closed to prevent R.F. communication signals from passing between transmission tracks interconnected by the gates, but which open in .
response to control input signals to the gates (herein, such gates are referred to as "transmission gates"). The transmission tracks are non-interfering in the sense that when a particular transmission track is carrying an R.F.
communication signal, it does not behave so as to cause electrical interference with co~munication signals being carried by other transmission tracks. The transmission tracks are interconnected by the transmission gates in a "branched path" manner which indicates that various optional paths branch off from the various tracks. More formally, the arrangement can be thought of in the following terms:
The pa-th rou-ting arrangement com.prises pluralities of each - of first, second and third transmission tracks. The plurality of first transmission tracks comprises a plurality of groups of first transmission tracks, and similarly, the plurality of second transmission tracks comprises a plurality of groups of second transmission tracks. For each pair of groups consisting of one of the groups of first transmission tracks and one of the groups of second transmission tracks, a unique one of the third transmission tracks is interconnected by ;~
transmission gates with every first transmission track in the group of first transmission tracks and with every second transmission track in the group of second transmission tracks. -The third transmission tracks are thus said to define branching paths between the first transmission tracks and the second transmission tracks. The path routing arrangement being so structured, a transmission path for R.F. communica-tion signals between any desired first transmission track and any desired second transmission track may be established via the unique third transmission track forming the branching path between the two desired tracks by opening the trans-mission gate interconnecting the desired first transmission track and the particular third transmission track and the transmission gate interconnecting the desired second transmission track and the particular third transmission track.
A transmission path having been so established, communication can take place between an R.F. communication terminal connected to the desired first transmission track and an R.F. communication terminal connected to the desired second transmission track. Where the communication terminals are R.F. receiver/transmitter terminals, such communication may be simultaneous bi-directional transmission, one of the two terminals transmitting on an R.F. carrier frequency which is divided in frequency from an R.F. carrier frequency . , .. . ...... ...... ,.. . ... , . . .,,, ,. . ~
on which the other terminal transmits. At the same time as such communication is taking place, communication may ; also take place between other desired pairs of communication terminals and in this regard there are two situations which may arise.
The first situation is that in which the branching path of the transmission path between one pair of terminals is separate from the branching path of the transmission path between another pair of terminals. In this situation, no portion of the transmission path between one pair of terminals is in common with the transmission path between the other pair of terminals. Owing to the substantially non-interfering characteristic of the transmission tracks generally, it will be readily apparent that communication between one pair of terminals may occupy the same or an ~-overlapping frequency band or bands as communication taking place between the other pair of terminals. Or, of course, the frequency bands may be completely different.
The second situation is that in which a portion of ~ ;
the branching path between one pair of terminals is in common with the branching path of the transmission path -between another pair of terminals. In this regard, it will be appreciated that the unique third transmission track which defines the branching path between any given "group"
(as the term is herein defined) of first transmission tracks and any given "group" of second transmission tracks is effectively common to all transmission tracks in both groups.
Thus, if one terminal of each pair of terminals is connected to separate first transmission tracks of the same group of first transmission tracks, and if the other terminal of each pair of terminals is connected to separate second transmisslon 1~84~33 tracks of the same group of second transmission tracks, then some portion of the transmission path between one pair of terminals is necessarily shared in common with some portion of the transmission path between the other pair of terminals. In this situation, communication may take place between each pair of terminals at the same time provided there is an appropriate selection of the carrier transmission frequencies associated with each terminal. For simultaneous bi-directional transmission between each pair of terminals at the same time, four separate carrier frequencies would be required. It will readily be apparent that additional pairs of terminals could communicate with each other at the same time sharing, in part, the same transmission path by the use of still further carrier frequencies appropriately divided in frequency from all other carrier frequencies.
However, it is to be understood that applications are envisaged where communication between more than one pair of terminals at the same time which would require the sharing of a portion of the same transmission path would not be permitted. ~ere it is contemplated that while a particular third transmission track is occupied (that is, once a transmission path has been established via the particular third transmission track between a given pair of terminals), then no other pair of terminals would be allowed to communicate using the particular third transmission track so long as it remained occupied. The result may be to prevent a desired transmission path from being established at a desired time ("blockage"). It must be remembered that in the case of reference to "blockage", this refers to equipment or route access only and not to busy or "don't answer"
1~84183 conditions at the called terminal. However, it is contemplated, particularly for relatively larse systems where communication takes place essentially between random pair of terminals at random times, that such blockage will be considered to be ~ -of only minor consequence.
Generally, it is contemplated that path routing arrangements in accordance with the present invention will be (though this is not necessary) characterized by a repetitiveness of structure. In this regard, it is contem-plated that the arrangement may comprise "gl" groups of first transmission tracks, each of which groups includes "tl" ~
first transmission tracks, and "g2" groups of second trans- ~ -mission tracks, each of which groups includes "t2" second transmission tracks, where "gl" and "g2" are each integer ;~
numbers greater than 1 and "tl" and "t2" are each integer .:
\
... _ .. ..
_ g _ ~84183 , numbers equal to or greater than 1. Thus, there are then ; "glxtl" first transmission tracks and "g2xt2" second transmission tracks. It may readily be determined that there will be "glxg2" third transmission tracks defining the branching paths between the "gl" groups of first transmission tracks and the "g2" groups of second transmission tracks. Also, it may readily be determined that a path routing arrangement so structured will have "glg2(tl + t2)"
transmission gates to allow a transmission path to be established between any desired one of the "glxtl" first transmission tracks and any desired one of the "g2xt2"
second transmission tracks. Such transmission path would be via the unique one of the "glxg2" third transmission tracks which interconnects the particular group of first transmission tracks of which group the desired first trans-mission track is a member, and the particular group of second transmission tracks of which group the desired second trans-mission track is a member.
In certain embodiments of the present invention, it is contemplated that the aforementioned integer numbers "gl", "g2", "tl", and "t2" will all be identical, say the integer number "n" ("n" being greater than 1). There will then be "n " first transmission tracks (i.e. "n" groups of "n" first transmission tracks), "n " second transmission tracks (i.e.
"n" groups of "n" second transmission tracks), "n " third transmission tracks, and "2n " transmission gates. Herein, a path routing arrangement so structured is characterized as being "symmetric". It is contemplated that such embodiments will be particularly suitable for a commu~ication system interconnecting "n2" subscriber communication terminals, 1(~8418;~
each subscriber cerminal beiny an R.F. communication -receiver/transmitter terminal connected to a unique one of the first transmission tracks of the path routing arrangement and to a unique one of the second transmission tracks of the path routing arrangement. According to this embodiment, any one of the subscriber terminals may communicate with any other one of the subscriber terminals.
It is contemplated that the connection between each i~
of such subscriber terminals and the transmission tracks may ~-include line equipment means having a calling mode of opera-tion and a called mode of operation, the terminal which initiates a call being referred to as the calling terminal and the terminal receiving the call being referred to as the called terminal. In the calling mode of operation, the line equipment means is for receiving R.F . communication signals as an input from the subscriber terminal and providing such communication signals as an input to the first transmission ;~
track to which the subscriber terminal is connected, and for receiving R.F. communication signals as an input from such -.~
first transmission track and providing such communication signals as an input to the subscriber terminal. In the called mode of operation, the line equipment means is for receiving R.F. communication signals as an input from the subscriber terminal and providing such communication signals as an input to the second transmission track to which the terminal is connected, and for receiving R.F. communication signals as an input from such second transmission track and providing such communication signals as an input to the subscriber terminal. ~hen communication takes place between a pair of terminals, one terminal would be in the calling 1~8418;~
mode of operation and the other terminal would be in the called mode of operation. The transmission path between the terminals can be considered as consisting of three portions: Vi2. a first portion between the calling terminal and its line equipment means, a second portion between the line equipment means of the calling terminal and the line equipment means of the called terminal, and a third portion between the line equipment means of the called terminal and the called terminal. The second portion of course comprises the transmission path through the path routing arrangement.
In one embodiment of the present invention, it is contemplated that the line equipment means of the terminals will include carrier frequency translation means for trans-lating the carrier frequency of R.F. communication signals ~-received as an input by the line equipment means. As will become more apparent hereinafter, the purpose of translating the carrier frequency is to produce a desired division between the carrier frequency of one R.F. communication signal and the carrier frequency of another R.F. communication signal, both of which signals are being transmitted at the same time over the previously mentioned first, second and third portions of the transmission path between the pair of terminals. For example, it is contemplated that in certain embodiments of the present invention, the system will comprise a plurality of subscriber communication terminals interconnected by the path routing arrangement so that bi~directional simultaneous transmission may take place between terminals.
According to such embodiments, it is contemplated that each terminal will be adapted to transmit on a predefined carrier frequency ana adapted to receive on a preclefined carrier frequency, the transmitting carrier frequency being divided in frequency from the receiving carrier frequency by a predetermined amount so that the transmitting and receiving frequency bands do not overlap. It is further contemplated that the predefined transmitting carrier ;~
frequency of any given terminal may be one of a relatively ;
- few (e.g. 10) possible transmitting carrier frequencies, -and not necessarily different than the transmitting carrier frequencies of all other terminals. Similarly, it is contemplated that the predefined receiving carrier frequency of any given terminal may be one of a relatively few (e.g. 10) possible receiving carrier frequencies, different than all of the possible transmitting carrier frequencies but not necessarily different than the receiving carrier frequency of all other terminals. In such cases, one way of maintaining a division of frequencies between communicating subscriber terminals is to include frequency translation means in the line equipment means of the terminals. Such frequency translation means may be operative as follows: (a) in the calling mode of operation: (i) to translate, if necessary, the carrier frequency of communication signals received as ;
an input from the second portion of the transmission path to the receiving carrier frequency of the calling terminal (which signals are then provided as an input to the calling terminal via the first portion of the transmission path), and, (ii) to provide as an input to the second portion of the transmission path, communication signals received from the calling terminal via the first portion of the transmission path (i.e. without frequency translation); and, (b) in the called mode of operation: (i) to translate the carrier frequency of communication signals received as an input from the second portion of the transmission path to the receiving carrier frequency of the called terminal (which signals are then provided as an input to the called terminal via the third portion of the transmission path), and, (ii) to translate the carrier frequency of communication signals received from the called terminal via the third portion of the transmission path to the receiving carrier frequency of the called terminal (which signals are then provided as an input to the second portion of the trans-mission path). Such provision for carrier frequency translation will maintain a division of frequency between carrier frequencies along the respective first, second, and third portions of the transmission path between the terminals, and at the same time will ensure that the communi-cation signals received by each terminal are on the carrier frequency which each terminal is adapted to receive. As will be appreciated by those skilled in the art, and as is discussed in more detail hereinafter, there are several ways other than the foregoing example whereby frequency translation means may be incorporated into the lines equipment means of a system for the purpose of maintaining a desired division of carrier frequencies over various portions of a transmission path between communication terminals Transmission tracks used in a path routing arrangement in accordance with the present invention are, as hereinbefore stated by definition, electrically unbalanced and substantially non-interfering R.~. transmission lines, conduits or the like.
The use of such transmission tracks permits the use of a branched path, path routing arrangement as an R.F. communication 1084~L83 routing device. Coaxial lines are an exemplary Eorm Of such transmission lines. They are unbalanced and the outer conductor of such lines provides a shielding effect and thereby contains R.F. communication signals so that that when such signals ;
are being transmi-tted on the line they will no~ substantially interfere with R.F. communication signals that are being transmitted on other lines which may be closely adjacent.
However, as will be apparent to those skilled in the art, the transmission tracks may have a structure other than -that of coaxial lines. For example, waveguides may be -`
used for transmission at microwave frequencies. (As a matter of economy, it is contemplated that waveguides would not be used unless the bandwidth requirements of the communication signals otherwise dictated.) The transmission gates of a path routing arrangement in accoxdance with the present invention may, as stated hereinbefore, be mechanical, electromechanical, or electrical (e.g. semiconductor or aiode) gates~ In one embodiment of the present invention, it is contemplated that such gates will be identified by a designated code and will include means for receiving a coded input signal, and, if the coded input signal received represents, in a selected code, the identification of the gate, for causing ~he gate to open and allow R.F. communication signals to pass bétween the transmission tracks interconnected by the gate. In a particular species of this embodiment, it is contemplated that a transmission gate will include means for detecting the coded input signal when such signal is applied as an input to a transmission track to which the gate connec_s. Such coded input signal may, for example, be provided to a ~ - 14a -1~84183 transmission track as modulated or unmodula-ted carrier signals having a frequency sufficiently high to propagate in the transmission track.
Of course, coded input signals to control trans-mission gates may be provided on control signal lines separate from the transmission tracks. Here r such control signals may, for example, be provided in digital form.
For example, the transmission gates may be identified by a binary-coded-decimal code, and the coded signals to control the gates provided in parallel or sequential order as inputs to the control signal lines which lead -to the gates. The implementation of such means for controlling transmission gates will be readily apparent to those skilled in the art.
Where the path routing arrangement is relatively small such as may be used in an inter-office communication system, it is conceivable that situations could arise where it may be desired to use manually operated mechanical transmission gates, e.g. a switch for making or breaking an electrical connection between transmission lines.
Branched path structures are, in a general sense, not new. In this regard, U. S. Patent No. 3,699,295 (Shinohara et al) which issued on October 17, 1972, may be of some interest in relation to the present invention.-This patent indicates that branched path structures per se are old and goes on to describe a particular arrangement for a branched path structure.
However, an important distinction is to be made between known branched path structures such as those disclosed or discussed in the Shinohara patent and branched ~ - 14b -1~84183 path structures in accordance with the present invention.
In contrast to the present invention, the transmission paths in the prior art structures are electrically balanced and are not particularly adapted for R. F. operation, and teach space divided, in contrast to frequency divided transmission paths for bi-directional operation (full duplex). Such transmission paths do not comprise "transmission tracks" as the term is herein defined. As a result of using electrically unbalanced, frequency divided, and substantially non-interfering R. F. transmission lines, conduits or the like, the present invention requires only one transmission gate at each branching point of the branched path structure and two gates for all terminal to terminal calls. Electrically balanced, branched path structures teach two gates or switches at each branching point and eight gates or switches for terminal to terminal calls.
The concept of performing, in a branched path, path routing arrangement (which may occupy a relatively small physical space), path routing operations for R. F.
communication signals being transmitted between pluralities of R. F. communication terminals (many of which terminals may be transmitting on the same carrier frequency), appears to be alien to the prior art. In addition, there appears to be no teaching in the prior art of the use of frequency division multiplexing in a branched path, path routing system. As will become more apparent hereinafter, for systems wherein a large number of communication terminals are interconnected, the combination of frequency division multiplexing and branched path routing permits a significant reduction in the number of R. F. communication channels of different frequency reasonably required to allow communications to take place between pluralities of desired pairs of the terminals at the same time.
\~
~ - 14c -1~84~83 The foregoing and other features of the present invention will now be described with reference to the drawings in which:
FIGURE 1 is a perspective view symbolically illustrating a portion of a branched path, path routing arrangement which may be used in a system inter-connecting 10,000 R.F. subscriber terminals.
FIGURE 2(a) symbolically illustrates one transmission path through the path routing arrangement of FIGURE 1.
].0 FIGURE 2(b) illustrates an alternate arrangement for one transmission path through a path routing arrangement generally similar to the path routing arrangement shown in FIGURE 1.
FIGURE 3 illustrates a typical interconnection between a portion of a cross horizontal transmission track of FIGURE 1 and back and front horizontal transmission tracks of FIGURE 1.
. FIGURE 4 illustrates a typical interconnection between a portion of a vertical transmission track of FIGURE 1 and front horizontal transmission tracks of FIGURE 1. ~-FIGURE 5 is a circuit diagram of a transmission gate which responds to input signals coded by audio tones and which signals are provided as an input to a :
transmission track.
FIGURE 5(a) illustrates a modification to the circuit of FIGURE 5 whereby the coded input signal is required to include additional audio tones to operate the transmission gate.
FIGURE 6 illustrates typical waveforms at various points during the operation of the circuit of FIGURE 5.
~ - 14d -~084183 FIGURE 7 is a portion of a circuit diagram of a simplified transmission gate.
FIGURE 8 illustrates a portion of a system incorporating the path routing arrangement of FIGURE 1 and interconnecting a plurality of audio/video subscriber terminals.
FIGURE 8(a) illustrates a variety of possible carrier frequency assignments along various portions of a bi-directional transmission path between a calling subscriber ter-minal and a called subscriber terminal.
FIGURE 9 is a circuit diagram of line equipment associated wlth a subscriber terminal in the system of FIGURE 8.
FIGURE 10 is a detailed circuit diagram of the calling control circuit of FIGURE 9.
FIGURE 11 is a detailed circuit diagram of the called control circuit of FIGURE 9.
FIGURE 12 is a circuit diagram of a circuit to automatically tune the frequency of a receiver to receive a desired frequency channel. , FIGURE 13(a) illustrates a modification to the circuit of FIGURE 9 to enable a calling party to identify itself to a called party.
FIGURE 13(b) illustrates a modification to the circuit of FIGURE 9 to enable a called party to receive a tone that identifies a calling party.
FIGURE 14 illustrates a conventional resistive hybrid circuit for the circuits of FIGURES 9 and 13(a).
FIGURE 15 is a circuit diagram of a diode transmission gate interconnecting two transmission tracks.
.
~ - 14e -1~84183 DETAILED DESCRIPTION
The detailed description which follows is primarily confined to a relatively large and symmetric branched path, path routing arrangement which may typically be used to interconnect a plurality of R.F. communication terminals so that communication links may be established via transmission paths defined through the arrangement between desired pairs of terminals. The path routing arrangement per se is - described in terms which contemplate the use of the arrangement in a subscriber communication system wherein simultaneous bi directional communication is to take place between pairs of subscriber terminals - one terminal of a pair being the terminal of a calling party, and the other terminal of a pair being the terminal of a called party. This description is then followed by a description of systems incorporating the path routing arrangement.
Referring now to the drawings, FIGURE l shows an illustrative embodiment, in simplified form, of a symmetric branched path, path routing arrangement l for providing bi-directional communication links via transmission paths defined through the arrangement between a plurality of ;-incoming lines and a plurality of outgoing lines. The communication links that are established will be between desired ones of the incoming lines (for example, line I
or line I9902) and desired ones of-the outgoing lines (for example, line 09901 or line 09997). An incoming line may be thought of as being associated with a calling party and an outgoing line may be thought of as being associated with a called party.
In the embodiment shown in FIG~RE l, it has been assumed for purposes of illustration that the path routing ~ - 14f - .
10~34183 operations are to be performed between lO,000 incoming bi-directional transmission lines Ioooo, Ioool, ..., Ig999, and lO,000 ou-tgoing bi-directional transmission lines 0000o/
0 0 999 (only lines Iolol~ I9902t 09901 09997 having been shown). The figure 10,000 is somewhat arbitrary but facilitates comparison with conventional lO,000 line switches used in conventional telephone systems. Also, as will become apparent, the selection of lO,000 permits a geometric order for the arrangement based upon the more familiar decimal system of counting.
Between any given incoming line I and any given outgoing line ~, a unique and self-contained transmission path may be established. Each such path includes a vertical trans-mission path V (e.g. Vl l)' a front horizontal transmission track F (e.g. Fl 99), a cross horizontal transmission track C
(e.g. Cg9 99), and a back horizontal transmission track B (e.g.
B99 99). Each such path also includes two transmission gates, namely, a "vertical" transmission gate GV (e.g. GVl l 99)' which is a transmission gate interconnecting a vertical trans-mission track and a front horizontal transmission track, and a "horizontal" transmission gate GH (e.g. GHl 99 97), which is a transmission gate interconnecting a front horizontal transmission track and a cross horizontal transmission track. In addition, each transmission path also includes a ~'slot" S (e.g. Sg9 99) ~-interconnecting the cross horizontal transmission track of the path and the back horizontal transmission track of the path.
A slot forms a direct electrical connection between the tracks it interconnects so that whenever a communication signal appears on one of the tracks it also appears on the other of the tracks.
Ideally, a slot presents no loss for communication signals.
J~ ' ' ~ - 14g -1~84183 The purpose of the slots is discussed hereinafter - they are not necessary elements of a branched path, path routing arrangement but they may serve to physically govern where transmission lines external to the arrangement (such as transmission line 0 in FIGURE 1) may be conveniently connected to the arrangement.
Thus, for example, the transmission path between line Iolol and line 09997 includes vertical transmission track Vl 1' vertical transmission gate GVl 1 99~ front horizontal transmission track Fl 99, horizontal transmission gate GHl 99 97, cross horizontal transmission track Cg9 97, slot Sg9 97 and back horizontal transmission track Bg9 97.
According to the terminology used in the introductory portion of this specification, a vertical transmission track may be considered as a "first" transmission track, a front horizontal transmission track may be considered as a "third" transmission track, and, a cross horizontal transmission track in combination with a slot and the back horizontal transmission track to which that slot interconnects may be considered as a "second" trans-mission track. In the latter case, for example, the combination of cross horizontal transmission track Cg9 99, back horizontal transmission track Bg9 99, and slot Sg9 99, can be considered as a "second" transmission track in accordance with the earlier terminology.
In general, as can be seen in FIGURE 1, the path routing arrangement comprises a vertical stack 8 of vertical platforms VPp(p=o~99) lying in y-z planes, and a horizontal stack 9 of horizontal platforms HPr (r=0,99) lying in x-z planes. The platforms provide rigidifying support for the transmission tracks and while not considered essential, are ~ - 14h -10~4183 considered desirable to import added mechanical strength and, as will be seen, to facilitate maintenance.
Each vertical platform VPp (p=0,99) includes a plur-ality of vertical transmission tracks Vpq (q=0,99) spaced parallel to each other and extending vertically on the platform (i.e. in the y-direction). Each horizontal platform HPr (r=0,99) includes a plurality of back horizontal transmission tracks Brs (s=0,99), a plurality of cross horizontal transmission tracks Crs (s=0,99), and a plurality of slots Srs (s=0,99).
The cross horizontal transmission tracks Crs are spaced parallel to each other and extend horizontally on the platform (i.e. in the x-direction). For each cross horizontal transmission track Crs, there is one corresponding slot Srs from which extends in the z-direction a corresponding back horizontal transmission track BrS. The slots of differing cross horizontal transmission tracks on the same platform are disposed relative to each other in the x-direction so that the corresponding back horizontal transmission tracks are evenly spaced in the x-direction.
For each pair of platforms consisting of a vertical platform VPp(p=o~99) and a horizontal platform HPr (r=0,99), there is a corresponding front horizontal transmission track Fpr which extends in the z-direction and interconnects with every vertical transmission track Vpq (q=0,'99) of the vertical platform VPp by means of a vertical transmission gate GVpqr (q=0,99) and with every cross horizontal transmission track Crs (s=0,99) of the horizontal platform HPr by means of a horizontal transmission gate GHprS (s=0,99). As can be seen in FIGURE 1, the portions of the front horizontal transmission tracks Epr on a horizontal platform HPr are interspaced with back horizontal transmission tracks BrS on the same platform.
~ - 14i -It should be noted that elemen-ts bearing the generalized subscripts p, q, r, and s are not shown as such in FIGURE 1.
Instead, only three vertical platforms VP0, VPl, and VPg9, and three horizontal platforms HPo, HP98, and HPg9, together with some of the transmission tracks, transmission gates and slots on each platform are shown. However, the basic geometry and overall structure of path routing arrangement 1 should be readily apparent upon consideration of FIGURE 1. Each vertical :~
platform VPp includes 10,000 vertical transmission gates GVpqr (q=0,99; r=0,99) forming a 100x100 matrix of interconnec- -tions between 100 vertical transmission tracks Vpq ~q=0,99) and 100 front horizontal transmission tracks Fpr (r=0,99); and, there are 100 vertical platforms VPp (p=0,99). Similarly, each horizontal platform HPr includes 10,000 horizontal transmission gates GHprS (p=0,99; s=0,99) forming a 100x100 matrix of inter-connections between 100 cross horizontal transmission tracks Crs (s=0,99) and 100 front horizontal transmission tracks Fpr (p=0,99); and, there are 100 horizontal platforms HPr (r=0,99).
On each hbrizontal platform HPr there are 100 slots Srs (s=0,99) forming a diagonal of interconnections between the 100 cross horizontal transmission tracks Crs (s=0,99) and the 100 back horizontal transmission tracks BrS (s=0,99) of the platform.
It will be recognized upon reference to FIGURE 1 that although a complete transmission path through path routing arrangement 1 between a given incoming line I and a given outgoing line ~ is unique, portions of the front horizontal transmission track which is part of such path are necessarily common to other transmission paths through the arrangement. For example, the portion of front horizontal transmission track Fl 99 between vertical transmission gate GVl 99 99 on vertical platform VPl ` ~08418~
and horizontal transmission gate GH1 99 0 on horizontal platform HPg9 is common to every path between vertical transmission tracks ~;~
Vl 0, V~ Vl 99 and cross horizontal transmission tracks Cgg o~ Cgg 1' --~ Cgg 99. ~, FIGURE 2(a) illustrates some additional aspects of the transmission paths of path routing arrangement 1 of FIGURE 1.
Ordinarily, the arrangement 1 will be contained in a rectangular ' enclosure which can be thought of as having a front wall 5 and a ,' back wall 7, each opposed on opposite sides of a stack dividing plane 6, which plane divides the vertical stack 8 from the horizontal stack 9. The vertical stack 8 is between the front :
wall 5 and the stack dividing, plane 6, and the horizontal stack 9 is between the back wall 7 and the stack dividing plane 6. ' ':
By way of example, FIGURE 2(a) shows the transmission path between incoming line Iolol and outgoing line 09997 and includes the specific elements Vl 1' Fl 99, Cg9 97, Bg9 97, GVl 1 99~ GHl 99 97, and Sg9 97 as are shown in FIGURE 1. In addition, the transmission path is now shown to include connectors ..
2, 3 and 4. Connectors 2 and 3 respectively serve the obvious purpose of means for connecting incoming line Iolol and outgoing ~ -line 09997 to the transmission path. Connector 4, which is , included as a part of front horizontal transmission track Fl 99, exemplifies a preference that the portion of a front horizontal transmission track on a vertical platform be separable from the corresponding portion of the front horizontal transmission track ;~
on a horizontal platform. Thereby, an'entire~.platform may~.readily be removed from the stack in which it appears;. This will facilitate maintenance or repair of transmission tracks or ~, :
transmission gates on the platform and will facilitate replace-ment of the platform.
~ - 14k -As is known, undes ~ re ~ ection of communication signals may be produced on an R. F. transmission line if the signals encounter an impedance mismatch. Various techniques for impedance matching are known in the art; the specific choice in any case will probably be governed by empirical considerations.
Such impedance matching devices and techniques are not within the scope of the present invention. In figure 2(a) the provision on respective tranmission tracks of impedance matching loads has been symbolically depicted by load terminations 11.
Each transmission track of path routing arrangement 1 may be coaxial line suitable to concurrently carry several R. F. communication channels, each channel having an associated carrier frequency and a predetermined bandwidth, the carrier frequencies of all channels being divided from each other by a predetermined amount so that the frequency bands of respective channels do not overlap. For purposes of illustration, it will be assumed that path routing arrangement 1 is for use in con-junction with an audio/video communications system wherein a communications signal entering the arrangement from an incoming line I may occupy any one of a first group of ten predetermined "LOW" channels, and wherein a communications signal entering the arrangement from an outgoing line ~ may occupy any one of a second group of ten predetermined "HIGH" channels; as follows:
\~
~ - 141 -~84183
3 120 3 220
4 130 4 230 7 160 7 260 :
8 170 8 27~ ' TABLE A
- 14m -1~34183 As is known, the loss per foot of coaxial line generally increases as frequency increases and generally decreases as the diameter of the line increases. Hence there will be a trade-off to be made between loss and the physical diameter of the tracks.
For the range of frequencies shown in Table ~ it is considered -that an 0.25 inch coaxial line with polyvinyl or polyethylene dielectric does not present undue loss.
As can be seen from Table A, each channel has..available a 10 MHZ baseband which is sufficient to allow, for example, the first 0 to 6 MHZ to be available for color video intelligence transmission and a 7.5 MHZ subcarrier to be available for audio subcarrier transmission.
The reasons for a selection of 20 channels as shown in Table A will become apparent hereinafter, but it is to be understood that a limitation to 20 channels is not a necessary limitation.
Thus, for example, on the transmission path between incoming line Iolol and outgoing line 09997 as shown in FIGURE I
or 2(a), a communications carrier occupying one channel could be ; 20 carried from line Iolol over vertical transmission track Vl 1 . to gate GVl 1 99; through gate GVl 1 99 (assuming the gate is : open); from gate GVl 1 99 over front horizontal transmission . track to gate GHl 99 97; through gate GHl 99 97 (assuming this gate is also open); from gate GHl 99 97 over cross horizontal -track Cg9 97 to slot Sg9 97; through slot Sg9 97; and from slot '~ Sg9 97 over back horizontal transmission track Bg9 97 to outgoing line 09997 - and, a communications carrier occupying another channel could be carried in the opposite dlrection from line ~9997 to line Iolol As may now be apparent, slot Sg9 97 and the corresponding back horizontal transmission track Bg9 97 merely serve to physical-ly orient the transmission path so that the connection of outgoing 1~8~183 line 09997 is through the back wall 7 (FIGURE 2(a)) of the path routing arrangement. The same is true of all slots Srs (r=o,99; s=0,99). The slots Srs (r=0,99; s=0,99) together with their corresponding back horizontal transmission tracks BrS (r=0,99; s=0,99) provides a possible means of mechanically directing each transmission path of the path routing arrangement 1 to the back wall.
A mechanical configuration for a slot for a coaxial line arrangement is shown in FIGURE 3 which, by way of example illustrates that portion of cross horizontal transmission track Cg9 99 extending from slot Sg9 99 associated therewith to horizontal gate GH96 99 99 also associated therewith. The view -shown may be considered as a section taken along the centre line of track Cg9 99 when looking at the path routing arrangement 1 of FIGURE 1 from the back. The inner conductor 20 of track -~
Cg9 99 is thus exposed to view. Likewise, end views of the inner conductors 20 of tracks Bg9 99~ F98 99~ B98 99~ F97 99, B97 99 and F96 99 are exposed to view.
As shown in FIGURE 3 the slots Sg9 99 merely comprise ;~
~20 an inner conductor 23 joining inner conductor 20 of track Cg9 99 to inner conductor 20 of track Bg9 99 and an outer conductor 22 joining outer conductor 21 of track Cg9 99 to outer conductor ~-q~i 21 of track Bg9 99. There is thus formed a direct low impedance electrical connection. In the z-direction (see FIGURE 1) the ` slots S98 99 and S97 99 are disposed behind track Cg9 99 and thus the inner conductors 23 of those slots only partially exposed in ;~ FIGURE 3. -. .
The horizontal transmission gates in FIGURE 3 are shown in a symbolic form and will be discussed in more detail hereinafter.
,.
1084183 1 ~
As an alternative to the use of slots and back horizontal transmission tracks, and assuming mechanical considera~
tions do not otherwise dictate, a cross horizontal transmission track may connect directly to an outgoing line. By way of example, FIGURE 2(b) illustrates cross horizontal transmission track Cg9 97 connecting directly through connector 3a at sidewall -7a to outgoing line ~9997. Although not shown in the drawlngs, it will also be appreciated that connection of an incoming line to a vertical track - rather than in the manner indicated in FIGURES 2(a) and 2(b) - could be by way of a slot interconnecting the vertical track and an additional transmission track extending from the slot to the front wall 5 (see FIGURE 2(a) or 2 (b)) to join the incoming line through a suitable connector.
Referring now to FIGURE 1, the vertical and horizontal transmission gates in the transmission path between a given incoming line and a given outgoing line are normally closed preventing the transmission path from passing communication carriers in either direction. A carrier communication link is established over the transmission path only if both the vertical transmission gate and the horizontal transmission gate are opened in response to suitable control signals.
The transmission gates ~f a path routing arrangement may comprise manually operated switches making or breaking an electrical connection between transmission tracks. However, particularly for large path routing arrangements compactly ar-ranged such as that shown in FIGURE 1, it is clearly preferable that the transmission gates be automatically remotely controlled.
~, There are of course various means whereby such control may be ~-achieved, but there is one particular method that does not 3~ require the use of separate control line inputs to the path .
1~8418:~ ~
.~ :
routing arrangement for the sole purpose of operating the ~
transmission gates. Instead, the gates between a particular 5 incoming line and a desired outgoing line may be controlled by a suitable control signal input from the incoming line to the vertical transmission track associated therewith. Electrical continuity exists in a transmission track of path routing arrangement l even if all transmission gates on the track -~
happen to be closed, thus, if such is the casel a control signal ~-input to the transmission track is nevertheless carried along the track and can be used to open a selected gate depending on ~
the character of the signal. Accordingly, for example, a ;
suitable control signal input from line Iolol in FIGURE 1, 2(a) or 2(b) to vertical transmission track Vl 1 could first travel along vertical transmission track Vl l to cause vertical transmission gate GV1 1 99 to open in response thereto, and r then continue along front horizontal transmission track Fl 99 to cause horizontal gate GHl 99 97 to open in response thereto.
v~ FIGURES 3 and 4 symbolically depict transmission gates . that open in response to suitable control signals carried by a transmission track. FIGURE 4 illustrates that portion of vertical r transmission track Vl 1 extending from vertical transmission gate GVl l 97 (not shown in FIGURE 1) to vertical transmission . .
`j gate GVl l 99 The view shown may be considered as a section taken along the centre line of track Vl l when looking at path routing arrangement l of FIGURE 1 from the front. The inner conductor 20 of track Vl l is thereby exposed to view as are end views of the inner conductors 20 of front horizontal transmission tracks Fl 97v Fl,98 and l,99 In the case of FIGURE 4, control signals to open a selected vertical gate are carried by vertical transmission 1~84183 ~
.
track Vl 1 Each vertical gate includes means responsive to open the gate if the control signal has the particular character to which the gate is designed to so respond. In FIGURE 4 the vertical gates are shown in their normally closed position - that is, there is no continuity between their gate contact line 24 -connected to inner conductor 20 of vertical transmission track Fl 1 and their gate contact line 25 connected to inner conductor 20 of the corresponding front horizontal transmission track Fl 97, Fl 98 or Fl 99, as the case may be. Thus in this condition, electrical signals are not able to pass from vertical transmission track Vl 1 to one of the front horizontal transmission tracks - shown.
~ Each vertical gate in FIGURE 4 is also shown to include :; , .
', a signal detection means or probe 86 which sehses the character ,~ of control signals that appear in vertical transmission track -~
~ Vl 1 In response to detection by the probe 86 of the appropriate 4~' ~ control signal for a given vertical gatef electrical continuity ;~ is formed between gate contact lines 24 and 25 of the particular ~j vertical gate. Then, the contact lines 24 and 25 of a particular ~
t~20 vertical gate, which contacts are symbolically spaced apart in `-FIGURE 4, can be thought of as symbolically joined to form a : .1 , .
direct electrical connect1on between inner conductor 20 of track Vl 1 and inner conductor 20 of the front horizontal transmission track corresponding to the particular vertical gate. Particular embodiments of transmission gates are discussed hereinafter.
For selectively opening any one of the 100 vertical transmission gates GVpqr (r=0,99) on a given vertical transmission track Vpq, it is necessary that each such gate be responsive to a control signal different from the control signals that open other ones of such gates. In other words, a control signal must be coded to open a particular vertical gate and the particular 1(3134183 gate must be coded to open in response to that particular cocled control signal.
~n the case of FIGUR~ 3, the control signals to open the horizontal gates are carried by the front horizon-tal trans-mission tracks assoeiated with the gates. Thus, for example, the eontrol signal to open horizontal gate G~I96 99 39 is earried by front horizontal transmission traek F96 99. Of course, this control signal will have gained access to traek F96 99 through - any one of the 100 vertlcal transmission gates GV96 q 99 (q=o, 0 99) interconnecting traek F96 99 with vertieal transmission traeks V96 q (q=0~99) on vertieal platform VP96.
Generally, the horizontal transmission gates are seleeted to open in the same manner as described for vertieal ; transmission gates. For seleetively opening any one of 100 horizontal transmission gates GHprS (s=0,99) on a given front horizontal transmission traek Fpr, it is necessary that eaeh such gate be eoded to open in response to a eoaed eontrol signal distinet from the eoded eontrol signals that open the other horizontal gates on the traek.
~o -Aecordingly, it will be eoneluded that to establish a desired eommunication link in the manner aforesaid, the eontrol signal input from an incoming line must be coded to open a partieular vertical gate and a partieular horizontal gate. One teehnique for eoding the control signal is to superimpose audio tones on predetermined control signal carrier rrequeneies, the tones being superimposed in a sequence representing the digits that iden-tify the outgoiny line with which it is desired to establish a communication link.
For purposes of illustration it will be assumed that 3 digits are represented by single frequency audio -tones as appears in Table B following:
- 2~ - :
1i~84183 TONE TONE
DIGITFREQ. (HZ) DIGIT FREQ. (HZ) 3 4600 8 5600 ;
TABLE B
The particular tones selected are so called "out-of-band" audio tones because, while they are within the audio range - i of frequencies, they are above the usual voice frequency range ;;~
j of many common telephone communications systems. --Tones to open vertical transmission gates will be superimposed on a 1 MHZ carrier frequency and tones to open hori- ~ -zontal transmission gates will be-superimposed on a 2 MHZ carrier . ", . , ' frequency. The selection of 1 MHZ and 2 MHZ carriers is made because these frequencies are outside the frequency range of the ~,l selected communications carriers (See Table A) and because the ~'`
l circuitry of the vertical and horizontal transmission gates can be 20 made much smaller in size than, for example, the circuitry that would be required to detect tones superimposed on the communication carriers which, as will be recalled, may occupy any one of ten channels together spanning a broad range of frequencies. Also,these frequencies are sufficiently high to avoid the generation of currents on the outer surface of the coaxial tracks causing interference. ~ ~-The selection of tone frequencies is somewhat arbitrar~.
The tones could, for example, lie in the voice frequency range rather than an out-of-band range and could, for example, comprise tones with two frequency components as are used in some common telephone systems. However, if voice frequency tones are used, additional care may be needed to ensure that the means providing the control signals to the path routing arrangement does not 1~84183 - behave in a manner such that undesirable false tones would be provided in response to voice frequency intelligence.
Referring now to FIGURE 1, 2(a~ or 2 (b), if, for example, the tones 5800 HZ and 5800 HZ appear in sequence (ie.
the digit sequence 9-9) superimposed on a 1 MHZ carrier frequency and then the tones 5800 HZ and 5400 HZ appear in sequence (ie.
the digit sequence 9-7) on a 2 MHZ carrier frequency, all of which appear as an input control signal from line Iolol to vertical transmission track Vl 1' then, the sequence 5800 HZ -5800 HZ
L0 -5800 HZ -5400 HZ (ie. 9-9-9-7) has identified outgoing line ~9997 If vertical transmission gate GVl 1 99 is coded to open in response to the digit sequence 9-9 on a 1 MHZ carrier and if horizontal transmission gate GHl 99 97 is coded to open in response to the digit sequence 9-7 on a 2 MHZ carrier, both gates will be open when the entire sequence 9-9-9-7 is completed and a link for carrier communications between incoming line Iolol and outgoing line ~9997 will thereby be established.
A circuit for a transmission gate which opens in response to suitable coded carrier signals appearing in a transmission track is shown in FIGURE 5. As will become apparent, the circuit also includes means to close the gate in response to suitable coded carrier signals appearing in the transmission track. Once having decided to use a transmission track to carry signals to open the gate it is considered that it would be preferable to also use means to close the gate in response to signals appearing in a transmission track. Of course, other means could be used.
Since the basic structure of every vertical and hori-zontal transmission track may be basically the same, TRACK 1 of FIGURE 5 may be considered as a vertical transmission track with TRACK 2 being a front horizontal transmission track, or, TRACK 1 1C~8~18~
may be considered as a front horizontal transmission track with TRACK 2 being a cross horizontal transmission track. If TRACK 1 is considered as a vertical transmission track, then code receiver 89 is tuned to receive 1 MHZ carrier frequencies as an input on line 88 from sensing coil 87 which detects signals on gate contact line 24. Similarly, if TRACK 2 is a front horizontal transmission F
track, then code receiver 89 is tuned to receive 2 MHZ carrier '',;' frequencies. In either case, the output of code receiver 89 on line 90 (which also appears on lines 94 and 95) is simply the ;~ 10 audio tone that is superimposed on the carrier.
The design of receivers such as code receiver 89 which received a modulated carrier frequency input signal and produce as an output the modulating frequency is very well known in the art and will not be discussed in detail. The same is true of many other circuit elements which will be referred to hereinafter with ~ -reference to FIGURE 5 and other FIGURES. These elements include receiver detectors (R/D) which receive an ac input and produce a dc logic signal as an output if the input frequency is the fre-quency or frequency range for which the receiver is tuned; flip-flops; multivibrators; and other common circuit elements.
Referring again to FIGURE 5, the normal condition of the circuit is that normally open switch SWl between gate contact lines 24 and 25 is open as shown. Thus the transmission gate as a whole is normally closed and does not permit electrical signals to pass between TRACK 1 and TRACK 2. Switch SWl remains open so long as the control signal input on line 100 to the switch control SWC, which control mechanically drives switch SWl, remains at logical 0. If such control signal input goes to logical 1, switch control SWC closes switch SW
making electrical contact between gate contact lines 24 and 25 and therefore between line 20 of TRACK 1 and line 20 of TRACK 2. The transmission gate is then open.
Detail "A" of FIGURE 5 illustrates a basic circuit to energize a relay coil C of switch control SWC to cause switch SWl to close. A logical 1 input to the base of transistor Ql causes transistor Ql to turn on. When transistor Ql is on, the , bias across resistor Rl produced by the voltage divider action of resistors Rl and R2 biases transistor Q2 on allowing current to flow from voltage source V+ through coil C energizing the L0 coil. The bottom plate P of switch SWl is then magnetically drawn towards coil C against the action of spring S attached to the plate P and the frame F of switch control SWC. When the input on line 100 goes to logical 0, transistors Ql and Q2 are off and the coil C is de-energized. Diode D suppresses inductive switching spikes on turn-off.
As can be seen in FIGURE 5, the circuit of the trans-mission gate includes three flip-flops FFl, FF2 and FF3. These -~
flip-flops are of the edge triggered set-reset variety each having a set input Sl, S2 or S3 as the case may be, a reset ~ input Rl, R2 or R3 as the case may be, and a set output Pl, P2 or P3 as the case may be. The logical state of a-set output depends on whether the flip-flop last received a set command on its set input or a reset command on its reset input. Herein, it is assumed that all set-reset flip-flops are so designed that a set or reset command, as the case may be, is a switching transition from logical 0 to logical 1.
The normal logical state of set outputs Pl, P2 and P3 of flip-flops FFl, FF2 and FF3 respectively is logical 0. As can be seen, the output P3 of flip-flop FF3 on line 99 is also 3~ one input of dual input logical "AND" gate ANDl. Thus, regardless 1~D84183 of the logical state of the other input to gate ANDl on line ~
100, switch SWl will be logical 0 of output P3 of flip-flop .
~F3 is logical 0.
The normal condition of switches SW2 and SW3 appearing in FIGURE 5 is also open. That is, when the input to switch SW2 from output Pl of flip-flop FFl on line 93 is logical 0, switch SW2 is open; when such input is logical 1, the switch ~`
~ is closed. Likewise, when the input to SW3 from output P2 - of flip-flop FF2 via lines 98 and 105 is logical 0, switch SW
is open; when such input is logical 1, the switch is closed.
The circuit of FIGURE 5 includes three receiver detectors R/Dl, R/D2, and R/D3, the first of which is for detecting the first audio tone of the two tones required to identify the gate, the second of which is for detecting the second audio tone of the two tones required to identify the gate, and - the third of which is for detecting a DISCONNECT tone to cause the transmission gate to be closed. In this case, it will be assumed that a disconnect tone is a 6000 HZ out-of-band tone.
When the proper tone frequency is on line 90 at the input of receiver detector R/Dl, on line 96 at the input of receiver detector R/D2, or on line 106 at the input of receiver detector R/D3, as the case may be, the output of the receiver detector is logical 1 - otherwise it is logical 0. Thus, for example, if the transmission gate is coded to detect the tone sequence 4600 HZ - 5400 HZ (ie. the digit sequence 3-7), receiver detector R/D~ is tuned to receive and detect a 4600 HZ tone and receiver detector R/D2 is tuned to receive and detect a 5400 HZ
tone. Receiver detector R/D3 is tuned to receive and detect a 6000 HZ tone. In each case it is assumed that all tones initially appear on the carrier frequency (1 MHZ or 2 MHZ, as the case may be) that code receiver 89 is tuned to receive.
1~84~8~
As will be seen, the receiver detectors RJDl to R/D3 and other receiver detectors referred to herein are used to ~ -' control the switching of flip-flops and in some cases to trigger ' one-shot multivibrators. Depending on the design of a receiver ' detector per se, the logical transition at its output in response to the beginning of or end of an ac signal at its input may not be sufficiently fast to cause switching or triggering of a fol-lowing flip-flop or multivibrator, as the case may be. Also, there may be undesirable ripple at the output of a receiver detector.
Accordingly, it may then be necessary to insert a threshold device (not shown) such as a Schmitt trigger at the output of ~;
the receiver detector.
To assist in describing the circuit shown in FI~URE 5, reference will be made to FIGURE 6 which shows typical waveforms at various points of the circuit. The DISCONNECT tone in FIGURE 6 is shown with dashed lines because the waveforms are ! indended to indicate response both with (solid lines) a DISCONNECT tone.
When the 4600 HZ first digit appears on line 90 at ~0 the input of receiver detector R/Dl, the output on line 91 to the input of logical inverter INVl goes to logical 1 as shown~
in FIGURE 6. The output of inverter INV3 on line 92 to input Sl of flip-flop FFl goes to logical 0, but since this is a negative going transition from logical 1 to logical 0 there is no response by flip-flop FFl. However, when the 4600 HZ tone terminates, the output of receiver detector R/Dl on line 31 returns to logical 0 and the output of inverter INV3 on line 92 returns to logical 1. Accordingly, there is a set command at the input Sl of flip-flop FFl and its output Pl on line 93 ,0 goes to logical 1 causing switch SW2 to close.
~084183 :~?
When the 5400 HZ second digit tone appears on line 96 at the input of receiver detector R/D2 (via lines 90, 94, 95 and switch SW3 which switch is now closed), the output on line !7",/ 97 to input S2 of flip-flop FF2 goes to logical 1. Such trans-.. ~ ition at the input S2 of flip-flop FF2 is a set command to flip-: . , flop FF2 and its output P2 on lines 98 and 105 goes to logical 1.
, It might be noted that there is no inverter between 'i .
the output of receiver detector R/D2 and the input S2 of flip-flop FF2 corresponding to inverter INV3 between the output of receiver detector R/Dl and input Sl of flip-flop FFl. Inverter INV3 performs a delay timing function that prevents switch - SW3 from closing before the first digit tone terminates. In this particular example where receiver detector R/D2 is tuned to a different frequency (5400 HZ) than the frequency (4600 HZ) to which receiver detector R/Dl is tuned, such a delay is not ~;
necessary and the output of R/Dl could be taken directly to the input Sl of flip-flop FFl. Switch SW2 would then close at the beginning of the 4600 HZ tone. This tone would then appear on :
line 96 at the input of receiver detector R/D2, but since R/D2 is not tuned to 4600 HZ, it would not respond. However, if the first and second digits that identified a transmission gate happened to be the same - for example 3-3 instead of 3-7 as in . the present case, then both flip-flops FFl and FF2 would be set :~ by the first tone because receiver detector R/D2 would respond.
Returning again to the sequence of operation, when the output P2 of flip-flop FF2 goes to logical 1, a set command is provided on line 98 to set input S3 of flip-flop FF3. Thus, as shown in FIGURE 6, the output P3 of flip-flop FF3 on line 99 goes to logical 1. If, as may occur, the output P3 of flip-flop FF3 was already at logical 1 then there would of course be no 1~8418~
change. Also, as shown in FIGURE 6 by the continuing solid line of the waveform for line 99, the output on line 99 remains at logical 1 so long as no DISCONNECT tone arrives. Assuming for the moment that the input on line 108 to gate AND1 is logical 1, the logical 1 condition on line 99 appears on line 100 causing switch SWl to close. The transmission gate is now open.
When the output P2 of flip-flop FF2 goes to logical 1, the output appears on line 105 via line 98 causing switch SW3 ;~
to close. If a 6000 HZ DISCONNECT tone then appears on line 90, it reaches the input of receiver detector R/D3 via line 94 and switch SW3 causing the output of R/D3 on line 107 to go to logical 1. This transition is received on line 107 as a reset command to reset input R3 of flip-flop FF3 which causes the output P3 of flip-flop FF3 on line 99 to go to logical 0 (shown by dashed lines for line 99 in FIGURE 6). This output also appears through gate ANDl on line 100 as the input to switch control SWC. Since switch SWl is open for a logical 0 input, the transmission gate will now be closed.
In summary, to open the transmission gate it is necessary to provide the tones 4600 HZ - 5400 HZ in sequence.
To close the gate it is necessary to provide the tones 4600 HZ - 5400 HZ - 6000 HZ in sequence. Nothing has yet been said about the timing of tones in the sequences.
To enable the transmission gate to detect recurring sequences of the tones 4600 HZ and 5400 HZ, a timing circuit is included which causes flip-flops FFl and FF2 to be reset a pre-determined time after the first tone (4600 HZ) of the sequence is detected. The basic elements of the timing circuit as shown in FIGURE 5 are one-shot multivibrator O/Sl and logical inverter INV4. It is assumed that one-short multivibrator O/Sl produces ~ lG84183 a Iogical 1 pulse having a predetermined pulse width in respon , ` !
s: to a negative going logical transition (logical 1 to logical 0) appearing at its input on line 101. The input on line 101 is also the output of inverter INV3 on line 92. The output of 0/S
is on line 102 to the input of inverter INV4, the output of which inverter on line 103 is also the input on line 104 to reset :~
inputs Rl, R2 of flip-flops FFl, FF2 respectively.
As will be seen, the effect of the timing circuit is that the se~uence of tones required to open or close the o transmissiOn gate must be completed within the duration of the logical 1 pulse of one shot multivibrator 0/Sl. Typically, the duration of a tone may be of the order of 50 milliseconds and tones may be spaced 50 milliseconds apart, thus, if the one-shot multivibrator is triggered when the first digit tone is first detected (as the circuit shown in FIGURE 5 is designed to do) rather than on termination of the first digit tone (as the circuit of FIGURE 5 could obviously be modified to do), a pulse duration of 250 milliseconds would suffice for the circuit of FIGURE 5 and leave a margin for timing fluctuations.
The operation of the timing circuit is as follows and again reference may be made to FIGURE 6. When the output of ~ !
inverter INV3 appearing on line 101 via line 92 goes from logical 1 to logical 0, one shot-multivibrator 0/Sl is triggered producing at its output on line 102 a logical 1 pulse as shown in FIGURE 6. The pulse width shown is somewhat greater in duration than need be and could terminate any time after the condition on line 99 as shown in FIGURE 6 goes to logical 0.
Since the output of INV4 on line 103 is the logical inverse of the condition on line 102, a logical 0 pulse appears on line 103. When the logical 0 pulse terminates a reset command 1~4183 is provided on line 104 from line 103 to the reset inputs Rl, R2 of flip-flops FFl, FF2 respectively. Accordingly, the outputs Pl, P2 of flip-flops FFl, FF2 respectively go to logical 0 as shown in FIGURE 6 and switches SW2, SW3 are opened.
A further characteristic of the transmission gate that results from use of the timing circuit is that if the required first digit tone does appear, but is followed by a second digit tone other than the required second digit tone, flip-flop FFl will only be set for the duration of the output pulse of one-shop multivibrator O/Sl.
It is preferable that some means be included to prevent the opening of a transmission gate under certain circumstances.
In FIGURE 5 busy circuit 110 is a means which prevents the closure of switch SWl if the condition on line 99 goes to logical 1 when an input to busy circuit 110 on BUSY LINE 109 is logical 1.
Busy circuit 110 includes buffer amplifier BUFFl, two logical inverters INVl and INV2 and field effect transistor FETl. When the condition on line 100 is logical 0, the output of inverter INV2 is logical 1 which closes FETl whereby the logical condition on BUSY LINE 109 becomes the input to inverter INVl. Unless the condition on line 109 is forced to logical 1 by an external source applied as an input to the line, the logical condition on the line will be logical 0. The output of inverter INVl on , line 108 will thus be logical 1. If the condition on line 109 is forced to logical 1, the output of INVl on line 108 will be logical 0 which in effect disables gate ANDl such that switch SWl cannot be closed even if the proper sequence of tones are received by the transmission gate.
If there is no disabling busy condition and line 100 does go to logical 1, FETl will be open because the input thereto -` -` 1884183 from inverter INV2 will be logical 0. The input to inverter INVl will be logical 0 independent of the condition on line 109, thus the condition on line 108 at the output of inverter INV
will be logical 1 (as is required to have the logical 1 condition at the output of gate AND1 on line 100). Through buffer amplifier BUFF1, the condition on line 109 becomes logical 1 which condition may become the "external source" referred to just previously except that it is the external source for corresponding BUSY LINES 109 of selected other transmission gates to which BUSY ~INE 109 of the particular transmission gate shown in FIGURE S is connected. ~ ;-As will be seen, it is contemplated that in some embodi-ments of the path routing arrangement 1, the selective closing of transmission gates may require that a transmission gate be ; completely identified on its particular platform. Two tone identification as just discussed merely identifies a front i;
horizontal transmission track on a given vertical platform. `
For example, the tone sequence 4600 HZ - 5400 HZ (digit sequence 3-7) may identify vertical transmission gate GVl 1 37 ~ that is, the 37th vertical transmission gate of vertical track Vl 1 on vertical platform VPl. However, this tone sequence also identifies 99 other vertical transmission gates GVl q 37 (q=0,2,3..,99) on the 99 other vertical transmission tracks Vl q (q=0,2,3,...,99) connecting to the same front horizontal transmission track Fl 99 on the same vertical platform VPl. To completely identify a vertical transmission gate on a given vertical platform (on which there are 10,000 gates), and assuming that tone sequences are used generally as aforesaid, then, a sequence of four tones will be sufficient. For example, the first two tones may identify the transmission gate for a given vertical transmission ~84183 track, the last two tones may identify the transmission track itself (which track, for a given vertical platform, is identified by the last two digits of the number that identifies the associated incoming line).
As shown in FIGURE 5(a), the circuit shown in FIGURE 5 may readily be modified to detect a sequence of more than two tones. FIGURE 5(a) repeats (with addition of a logical inverter INV5) the portion of FIGURE 5 that detects the second tone of a sequence (indicated in FIGURE 5(a) as STAGE 2) and the portion of FIGURE 5 that detects a DISCONNECT tone on completion of a proper preceding sequence of tones. Elements of FIGURE 5(a) corresponding to elements of FIGURE 5 have been identified by the same characters. FIGURE 5(a) shows in addition STAGES 3...N
which stages are identical in structure to STAGE 2 and respond in the same manner as STAGE 2 except that their respective receiver detectors are tuned to respond to audio tones (ie. Table B tones) that may be different than the audio tone to which STAGE 2 responds.
Thus, for example, when the output of flip-flop FF2 appearing at terminal y of STAGE 2 in FIGURE 5(a) is logical 1 (which by reason of INV5, occurs at the termination of a tone detected by receiver detector R/D2), the switch in STAGE 3 corresponding to switch SW2 in STAGE 2 will be closed by such logical 1 output when it appears on line 93-3 at terminal x of STAGE 3. A proper tone appearing on line 95-3 at terminal u of STAGE 3 will, when it terminates, cause to be set the flip-flop in STAGE 3 corresponding to flip-flop FF2 in STAGE 2.
The output of STAGE 3 at terminal y will then be logical 1 and the next stage, if any, will then be conditioned to detect the next proper tone of the sequence. Of course, if four tones are to be detected, then four stages (N=4) are required.
1~84~3 The output at terminal y of the last stage. STAGE N, provides the set command on line 98 to flip-flop FF3. As can be inferred from FIGURE 5(a), the reset inputs of the flip-flops in STAGES 2 to N are connected by a cbmmon line 104, thus, the flip-flop of all stages are reset simultaneously by a logical 0 to logical 1 transition on line 103. One shot multivibrator 0/Sl (not shown in FIGURE 5(a)) must of course have a pulse width sufficiently broad to ensure that complete sequences of tones can be detected.
Thus, for example, and assuming that the tones identi-fying the front horizontal track precede the tones identifying the vertical transmission track, then, the required sequence of tones to open vertical transmission gate GVl 1 37 would be 4600 HZ - 5400 HZ - 4000 HZ - 4200 HZ (digit sequence 3-7-0-1).
To close the gate would require the same sequence followed by a :
6000 HZ DISCONNECT tone.
FIGURE 7 illustrates a more basic transmission gate circuit which does not incorporate a timing circuit and does not require a DISCONNECT tone to be first preceded by the two-tone sequence required to open the gate. Only a portion of the circuit has been shown but it may be thought of as replacing all circuitry in FIGURE 5 between the output of code receiver 89 and the line 99 input to gate ANDl in FIGURE 5. As can be seen, what is shown in FIGURE 7 includes many of the same elements as shown in FIGURE 5 interconnected in a very similar manner as in FIGURE 5, but excludes many other elements. One additional element, inverter INV6 is included.
The sequential operation of flip-flops FFl and FF2 in FIGURE 7 to cause a logical 1 condition to appear on line 99 at the output P2 of flip-flop FF2 is identical to the sequential ~ 84~.83 :
operation of flip-flops FFl and FF2 in FIGURE 5 to cause a logical 1 condition to appear on line 98 in FIGURE 5. However, flip-flops FFl and FF2 in FIGURE 7 are not automatically reset within a predetermined time after the proper first digit tone is detected by receiver-detector R/Dl in FIGURE 7. Instead, they are reset directly by receiver detector R/D3 when it receives at its input on line 94 a disconnect tone and in response produces at its output on line 114 a logical 1 condition which is the input to inverter INV6. The output of INV6 on line 115 then goes to logical 0. When the disconnect tone terminates, the output of INV6 on line 115 returns to logical 1. The transition from log-ical O to logical 1 on line 115 appears as a reset command to re-set inputs Rl, R2 of flip-flops FFl, FF2 respectively. Since a switch does not appear before the input of receiver detector R/D3 (contrary; to the case in the circuit of FIGURE 5), a reset command will result whenever a disconnect tone appears on line 90 at the output of code receiver 89. The reason that the circuit is designed to reset flip-flop FF2 at the termination of a disconnect tone rather than the beginning is that the disconnect tone will ordinarily cause closure of two transmission gates -one vertical transmission gate and one horizontal transmission gate - it being superimposed on both a 1 MHZ and 2 MHZ carrier.
If the external sources are controlled such that the carriers only enter on the incoming line (they could enter from an out-going line after a communication link was established) and assuming that the disconnect tone is simultaneously imposed on both the 1 MHZ carrier and the 2 MHZ carrier, then the possibi-lity exists that thevertical gate will close before the hori-zontal gate can respond if the vertical gate closes at the beginning of the disconnect tone.
A variety of circuit structures to effect theopening and closing of gates by use control signal inputs from the ~841B3 transmission path are possible and will occur to those skilled in the art. As will be seen, a particular structure may possess characteristics which impose practical limitations on the use to which the path routing arrangement in which the circuits are used is put depending on line or terminal equipment in associa-tion with which the path routing arrangement is used. Likewise, the transmission gates could be designed to respond to code signals other than the particular code signals selected. In the circuits represented by FIGURES 5 and 7, two audio tones in proper sequence are required to identify the transmission gate.
Theoretically one tone could be used to identify a particular transmission gate, but in a path routing arrangement where 100 transmission gates appear on a transmission track, 100 separate tones would have to be used if only one carrier frequency was used to carry code tones for transmission gates on that track. However, it would be possible to use different carrier frequencies for different groups of gates on the same transmission track and at the same time use ten or some other number of superimposed tones on those carrier frequencies. For example, for a transmission track providing control signals to 100 transmission gates, one of twenty tones on one of five carriers would be sufficient to uniquely identify each trans-mission gate on the particular track. Of course, this would not uniquely identify a gate on a platform having 100 tracks. In theory, it would be possible to use unmodulated carriers coded by selection of carrier frequency. For example, 1.0 MHZ might represent the digit 0, 1.1 MHZ the digit 1, 1.2 MHZ the digit 2, and so on.
All the foregoing is predicated by the comment made earlier that the control signals for transmission gates need not be carried by the transmission tracks. For example, switch SWl 1~84~83 ln FIGURE 5 could be controlled by purely digital means responsive to serial or parallel logic control signals (or a combination of serial and parallel logic control signals, which means would receive its logic inputs from circuit lines other than the transmission tracks. The techniques to open a switch by a circuit that is selectively responsive to one of many possible digital logic input combinations appearing on one (ie. completely serial logic) or more input lines are well known and need not be discussed in any detail. The logic signal 0 inputs may, for example be binary, or binary coded decimal or some other digital code. If the particular logic signal inputs happen to be the matching combination for which the transmission gate circuit is coded, then the gate clos~s.
The use of transmission gates having the circuit structures shown in FIGURES 5 and 7 will now be described with reference to path routing arrangement 1 of FIGURE 1.
Where the path routing arrangement 1 incorporates transmission gates such as that shown in FIGURE 7, it is preferable to ensure that once a bi-directional link is established o between any given ingoing line and any given outcoming line that no signal from any other incoming line be allowed access to any transmission track of the bi-directional link. The reason is that unless some means external to the path routing arrange-ment is used to prevent a DISCONNECT tone from entering on a second, third, etc. incoming line, the link may be prematurely terminated. A 6000 HZ tone will cause closure of any gate, the code receiver of which is tuned to the 1 MHZ or 2 MHZ carrier, as the case may be. If some such external means is included, then the subsequent incoming line from which access was gained will continue to have access after it would otherwise have pro-1~84183 vided a DISCONNECT tone and until a DISCONNECT tone is forth-coming from another source.
To deny access to signals from incoming lines other than the incoming line which forms part of the link, requires the disabling of all vertical transmission gates which connect to the front horizontal track of the link, and of all horizontal transmission gates which connect to the cross horizontal track of the link (other than the one vertical transmission gate and one horizontal transmission gate that are part of the link).
Assume, for example, that in FIGURE 1 a communication link has been established between incoming line lolol and out-going line ~9997. Then, vertical transmission gate GVl,l,gg and horizontal transmission gate GHl 99 97 are open. The gates which are to be disabled are horizontal transmission gates GHp 99 97 (p = 0,2,3, .... 99) and vertical transmission gates -~
GVl 99 (q = 0, 2, 3, ..... .99). If the transmission gate structure shown in FIGURE 7 is used for the vertical and hori-zontal transmission gates, and assuming the BUSY CIRCUIT 110 of - FIGURE 5 is incorporated, then the desired disabling function is achieved if BUSY LINE 109 of each horizontal gate GHp 99 97 (p = 0,99) is connected to the BUSY LINE 109 of every other horizontal gate GHp 99 97 (p = 0,99) and if the BUSY LINE 109 of each vertical gate GVl q 99 (q = 0,99) is connected to the BUSY LINE 109 of every other vertical gate GVl q 99 (q = 0,99).
When transmission gates of path routing arrangement 1 are dis-abled in the manner just described, it becomes evident that when a transmission path is established and in use, only two of the assumed 20 possible communication channels may be occupied in the transmission path (see Table A). As will become apparent, this is a somewhat inefficient use of the path routing arrange-ment.
.
..
1~841~33 It will be appreciated that a significant amount of potential blockage is present in the embodiment just considered.
For the particular example, no other incoming line to vertical platform VPl of FIGURE 1 can gain access to any outgoing line of horizontal platform HPg9, including outgoing line ~9997 which was the outgoing line in use. The reason is that incoming lines to vertical platform VPl can only gain access to horizontal platform HP99 by way of front horizontal transmission track Fl 99 through vertical gates GVl q 99 (q = 0 99) If transmission gates such as the transmission gate shown in FIGURE 5 are used for horizontal transmission gates; -and, transmission gates such as the transmission gate shown in FIGURE 5(a) having four STAGES (i.e. N=4) are used for vertical transmission gates, then, the amount of blockage can be reduced.
It is implicit that reduction in blockage requires that any given front horizontal transmission path may form part of more than one bi-directional communication link at one time.
Hence the task is now to ensure that the same channel is not occupied in more than one bi-directional link. This requires ~0 knowledge of the channels that will be occupied during any given bi-directional link. There are various ways in which the channels that will be occupied can be predetermined depending on the characteristics of equipment external to the path routing arrangement connecting to the incoming and outgoing lines.
One way to assign channels is to require that a communication signal from a given incoming line to any desired outgoing line always be in a channel determined by the identifi-cation of the incoming line and that a communication signal back from the desired outgoing line to the given incoming line always be in a channel determined by the identification of the outgoing 11~84~83 line. Alternately channels may be assigned by requiring that the communication signals from a given incoming line to any desired outgoing line and from the desired outgoing line to the `
given incoming line be in separate channels both of which are determined by the identification of the incoming line.
In the following discussion, it is assumed that the channel for a communication carrier from an incoming line is assigned depending on the last digit of the number identifying the incoming line. Thus, for example, communication signals from incoming line lolol to path routing arrangement 1 of FIGURE 1 are conditioned in advance to occupy channel 1 LOW - the carrier frequency being 100 MH~ (see Table A). Likewise, for example, communication signals from outgoing line ~9997 to path routing arrangement 1 are conditioned in advance to occupy channel 7 HIGH - the carrier frequency being 260 MH~ (see Table A). If a bi-directional link is established between line lolol and line , channel 1 LOW and channel 7 HIGH are occupied on front horizontal transmission track Fl 99. Hence it is necessary to deny access to track Fl 99 from any other incoming line from which signals occupying channel 1 LOW would arrive. On vertical platform VPl, signals arriving from incoming lines l (x = 0,9) would occupy channel 1 LOW, thus, for this example, it is necessary to deny access to incoming lines lolXl (x = ~`
0,2,3, ..., 9). Using the transmission gate of FIGURE 5, this result is achieved if the BUSY LINE 109 of each vertical trans-mission gate GVl xl 99 (x = 0,9) is connected to the BUSY LINE
109 of every other vertical transmission gate GVl,Xl,gg (x = 0,9).
Likewise, it is necessary to deny access to track ; Fl 99 from any outgoing line other than line ~9997 from which signals occupying channel 7 HIGH would arrive. On horizontal ., .
~34~83 platform HPg9, signals arriving from outgoing line ~99y7 (y = 0,9) would occupy channel 7 HIGH thus, for this example, -it is necessary to deny access to outgoing lines ~99y7 (y = 0,8).
Using the transmission gate of FIGURE 5(a), this result is achieved if the BUSY LINE 109 (not shown in FIGURE 5(a), of each horizontal transmission gate GHl 99 y7 (y = 0-9) is connected to the BUSY LINE 109 of every other horizontal transmission gate GHl 99 y7 (y = 0,9). At the same time all access to outgoing : line ~9997 through front horizontal transmission tracks other than front horizontal transmission track Fl 99 is denied by the connection of the BUSY LINE 109 of each horizontal transmission gate GHp,gg,g7 (p = 0,99) to the BUSY LINE 109 of every other horizontal transmission gate GHp 99 97 (p = 0,99).
Of course, the same BUSY LINE connections are made, mutatis mutandis, throughout path routing arrangement 1.
If all vertical transmission gates were merely identified by two tones, then, on a control signal sequence to close a given vertical transmission gate on a given front hor-izontal transmission track, all other open vertical transmission gates on the same front horizontal transmission track would close since such other vertical transmission gates are coded for the same two tones. To avoid such undesirable response, it is nec-essary to code the vertical transmission gates on a given front horizontal transmission track not only in respect of the front horizontal transmission track with which they are associated, but also in respect of the incoming line from which the control sig-nals are received. As has been said, on a given vertical plat-form, a vertical transmission gate is completely identified if it is identified by the last two digits of the number which identifies the incoming line from which the gate received control signals .~
'',' 1~84183 and by the last two digits ~f the number which identifies the front horizontal track to which the gate connects ~a leading 0 being added to this last number if necessary - for example, for front horizontal transmission track F21 8' (not shown in FIGURE 1), the last two digits are to be taken as 08 and not 18).
The operation of path routing arrangement 1 of FIGURE 1 using transmission gates as shown in FIGURE 5 for horizontal transmission gates and transmission gates as shown in FIGURE 5(a) for vertical transmission gates will now be considered by way of example. Firstly, the establishment of a bi-directional link between incoming line Iolol and outgoing line ~ggg7 will be con-sidered.
To give itself access to front horizontal transmission track Fl 99, incoming line Iolol must provide within the proper time interval the control signal sequence 5800 HZ - 5800 HZ
4000 HZ - 4200 HZ (digit sequence 9-9-0~1) on a 1 MHZ carrier.
If vertical transmission gate GVl 1 99 is not disabled by a busy signal on its BUSY LINE-109, then gate GVl 1 99 will open in response to such sequence. Control signals from incoming line Iolol may now travel down front horizontal transmission track Fl~gg~ ' :
; '~o give access to cross horizontal transmission track Cg9 97 from track Fl 99, incoming line Iolol must now provide within the proper time interval the control signal sequence 5800 HZ - 5400 HZ (representing the digit sequence 9-7) on a 2 MHZ carrier. If horizontal transmission gate GHl 99 97 is not disabled by a busy signal or its BUSY LINE 109, then gate GHl 99 97 will open in response to the sequence. Access would then be gained to cross horizontal transmission track Cgg 97 and 30 necessarily to outgoing line ~9997 through slot Sg9 97 and back horizontal transmission track B99 97. Outgoing line ~9997 would have access to incoming line 10101in the opposite direction over the now established path.
If horizontal transmission gate GHl 99 97 had been disabled by a busy signal on its BUSY LINE 109, the access gained to front horizontal transmission track may be terminated if line lolol provides within the proper time interval the control sig-nal sequence 5800 HZ - 5800 HZ - 4000 HZ- 4200 HZ - 6000 HZ
(representing the digit sequence 9-9-0-1 followed by the DIscoNNEcTtone) on a 1 MHZ carrier. The non-establishment of such access might be determined by external equipment (not shown in FIGURE 1) assoclated with incoming line lolol by thenon-receipt of a signal from line ~9997indicating that access had been established.
The non-establishment of access to front horizontal transmission track Fl ggcould be determined in a similar manner.
If a complete bi-directional link between lines lolol and ~9997 is established, it may be terminated by proper control signals within the proper time interval from either the incoming line or the outgoing line or both. If the control signals are to be provided from incoming line lolol the complete sequence 5800 HZ - 5400 HZ - 6000 HZ (9-7-DISCONNECT) on a 2 MHZ carrier to close horizontal gate GHl 99 gj; then 5800 HZ - 5800 HZ -4000 HZ - 4200 HZ - 6000 HZ (9-9-0-1-DISCONNECT) on a 1 MHZ
carrier to close vertical- gate GVl 1 99- The vertical gate must not be closed before the horizontal gate. If the control sig-nals are to be provided from outgoing line ~9997 the complete sequence is 5800 HZ -5800 HZ - 4200 HZ - 6000 HZ (9-9-0-1-DISCON-NECT) on a 1 MHZ carrier to close vertical gate GVl 1 99, then 5800 HZ - 5400 HZ - 6000 HZ - (9-7-DISCONNECT) on a 2 MHZ carrier to close horizontal gate GHl,gg 97. In this instance,the horizontal . ~ , ' . ~
1~84183 :.
gate must not be closed before the vertical gate. If -the control signals are provided from both lines, then of course the sequence of gate closure is not crucial.
It will now be assumed that a bi-directional link between incoming line Iolol and outgoing line ~99~7 has been established. Channel 1 LOW from line Iolol to line 09997 is occupied and channel 7 HIGH from line ~9997 to line Iglol is occupied. No incoming line to vertical platform VPl in FIGURE
1 having as a last dig~t identification the number "1" can gain access to horizontal transmission track ~1 99 Likewise, no incoming line to vertical platform VPl that has as a last digit identification a number other than "l",an~ which does again access to track Fl 99, can gain access to any cross horizontal trans-mission track having as a last digit identification the number "7" (except, as will be discussed track ~99 97 associated with outgoing line ~9997). Front horizontal transmission track Fl 99 can still be used in a bi-directional link between an incoming line having a last digit identification other than "1" and an outgoing line having a last digit identification ,j~20 other than "7". If a second bi-directional link is established subject to these conditions, then, similar conditions apply for ;~ a third link, a fourth link, and up to ten links for the twenty channels assumed. If ten links are formed then the last digit identification of each of the ten incoming lines will differ - from each other, and the last digit identification of each of the ten outgoing lines will differ from each other. For example, front horizontal transmission track Fl 99 might form part of the bi-directional link between the following pairs of lines at the same time:
. .
;LINE``~AI~g ~ CHA~æ~S;~q 0101 ~9997 1 LOW - 7 HIGH
(2) I - ~ 2 LOW - 8 HIGH
(3) I0173 ~9939 3 LOW - 9 HIGH
(4) I0104 ~9940 4 LOW - 0 HIGH
(5~ I0185 ~9951 5 LOW - 1 HIGH
(6) I - ~ 82 6 LOW - 2 HIGH
~7) Iol47 ~9903 7 LOW - 3 HIGH
(8) I - ~ s~ LOW - 4 HIGH
10(9) I - ~ 9 LOW - 5 HIGH
(10) I - ~ O LOW - 6 HIGH
, ,~
TABLE C
- It will be appreclated that the concurrent presence of more than one bi-directional link through a given front ~ :
: horizontal transmission tracX will mean that an incoming line~or : an outgoing line will necessarily receive from the path routing arrangement all channels from the other incoming and outgoing ` lines which lines connect through the same front horizontal transmission track. For example, referring to TABLE C, incoming .. :~
~ 20 line Iolol would not only receive channel 7 HIGH from outgoing `.
`:s~ line ~9997 but also would receive channels 0 to 6 and 8 HIGH
. from the other outgoing lines and would receive channels 0, and :: . r~
2-9 LOW from the other incoming lines because paths would be .'' defined from one incoming line to others. For example, the path between incoming line Iol22 (see TABLE C) and incoming line Iolol would be defined by vertical transmission track Vl 22 (not shown);.the portion of front horizontal transmission '; .
J track ~1 gg between vertical gate GVl 22 g9(not shown) and ~ :
vertical gate GVl 1 99; and vertical transmission track Vl 1 ``
. 30 It is contemplated that the external equipment (not shown) that .
. ' "~ ;:
-44- ` ~
:~ .
1 .
1{~84183 may receive multiple channels from incominy and outgoing lines -~
ill include means to discriminate signals on a particular channel and heavily attenuate signals on other channels -which it does no-t desire to receive.
There is a situation which has not been considered and that is where, for example, there is a bi-directional link between incoming line Iolol and outgoing line 09997 and an attempt is made to establish a bi-directional link between some other incoming line and outgoing line 09997 using front , 10 horizontal transmission track Fl 99. Say, for example $hat the attempted link was between incoming line Iol25 (not shown) `-and outgoing line 09997. Incoming line Iol25 would first provide the control signal sequence 5800 HZ - ~800 HZ - 4400 HZ -5000 HZ (digit sequence 9-9-2-5) on a 1 MHZ carrier the~eby giving access to track Fl 99 through vertical transmission track Vl 25 and vertical transmission gate GVl 25 99 and would then
8 170 8 27~ ' TABLE A
- 14m -1~34183 As is known, the loss per foot of coaxial line generally increases as frequency increases and generally decreases as the diameter of the line increases. Hence there will be a trade-off to be made between loss and the physical diameter of the tracks.
For the range of frequencies shown in Table ~ it is considered -that an 0.25 inch coaxial line with polyvinyl or polyethylene dielectric does not present undue loss.
As can be seen from Table A, each channel has..available a 10 MHZ baseband which is sufficient to allow, for example, the first 0 to 6 MHZ to be available for color video intelligence transmission and a 7.5 MHZ subcarrier to be available for audio subcarrier transmission.
The reasons for a selection of 20 channels as shown in Table A will become apparent hereinafter, but it is to be understood that a limitation to 20 channels is not a necessary limitation.
Thus, for example, on the transmission path between incoming line Iolol and outgoing line 09997 as shown in FIGURE I
or 2(a), a communications carrier occupying one channel could be ; 20 carried from line Iolol over vertical transmission track Vl 1 . to gate GVl 1 99; through gate GVl 1 99 (assuming the gate is : open); from gate GVl 1 99 over front horizontal transmission . track to gate GHl 99 97; through gate GHl 99 97 (assuming this gate is also open); from gate GHl 99 97 over cross horizontal -track Cg9 97 to slot Sg9 97; through slot Sg9 97; and from slot '~ Sg9 97 over back horizontal transmission track Bg9 97 to outgoing line 09997 - and, a communications carrier occupying another channel could be carried in the opposite dlrection from line ~9997 to line Iolol As may now be apparent, slot Sg9 97 and the corresponding back horizontal transmission track Bg9 97 merely serve to physical-ly orient the transmission path so that the connection of outgoing 1~8~183 line 09997 is through the back wall 7 (FIGURE 2(a)) of the path routing arrangement. The same is true of all slots Srs (r=o,99; s=0,99). The slots Srs (r=0,99; s=0,99) together with their corresponding back horizontal transmission tracks BrS (r=0,99; s=0,99) provides a possible means of mechanically directing each transmission path of the path routing arrangement 1 to the back wall.
A mechanical configuration for a slot for a coaxial line arrangement is shown in FIGURE 3 which, by way of example illustrates that portion of cross horizontal transmission track Cg9 99 extending from slot Sg9 99 associated therewith to horizontal gate GH96 99 99 also associated therewith. The view -shown may be considered as a section taken along the centre line of track Cg9 99 when looking at the path routing arrangement 1 of FIGURE 1 from the back. The inner conductor 20 of track -~
Cg9 99 is thus exposed to view. Likewise, end views of the inner conductors 20 of tracks Bg9 99~ F98 99~ B98 99~ F97 99, B97 99 and F96 99 are exposed to view.
As shown in FIGURE 3 the slots Sg9 99 merely comprise ;~
~20 an inner conductor 23 joining inner conductor 20 of track Cg9 99 to inner conductor 20 of track Bg9 99 and an outer conductor 22 joining outer conductor 21 of track Cg9 99 to outer conductor ~-q~i 21 of track Bg9 99. There is thus formed a direct low impedance electrical connection. In the z-direction (see FIGURE 1) the ` slots S98 99 and S97 99 are disposed behind track Cg9 99 and thus the inner conductors 23 of those slots only partially exposed in ;~ FIGURE 3. -. .
The horizontal transmission gates in FIGURE 3 are shown in a symbolic form and will be discussed in more detail hereinafter.
,.
1084183 1 ~
As an alternative to the use of slots and back horizontal transmission tracks, and assuming mechanical considera~
tions do not otherwise dictate, a cross horizontal transmission track may connect directly to an outgoing line. By way of example, FIGURE 2(b) illustrates cross horizontal transmission track Cg9 97 connecting directly through connector 3a at sidewall -7a to outgoing line ~9997. Although not shown in the drawlngs, it will also be appreciated that connection of an incoming line to a vertical track - rather than in the manner indicated in FIGURES 2(a) and 2(b) - could be by way of a slot interconnecting the vertical track and an additional transmission track extending from the slot to the front wall 5 (see FIGURE 2(a) or 2 (b)) to join the incoming line through a suitable connector.
Referring now to FIGURE 1, the vertical and horizontal transmission gates in the transmission path between a given incoming line and a given outgoing line are normally closed preventing the transmission path from passing communication carriers in either direction. A carrier communication link is established over the transmission path only if both the vertical transmission gate and the horizontal transmission gate are opened in response to suitable control signals.
The transmission gates ~f a path routing arrangement may comprise manually operated switches making or breaking an electrical connection between transmission tracks. However, particularly for large path routing arrangements compactly ar-ranged such as that shown in FIGURE 1, it is clearly preferable that the transmission gates be automatically remotely controlled.
~, There are of course various means whereby such control may be ~-achieved, but there is one particular method that does not 3~ require the use of separate control line inputs to the path .
1~8418:~ ~
.~ :
routing arrangement for the sole purpose of operating the ~
transmission gates. Instead, the gates between a particular 5 incoming line and a desired outgoing line may be controlled by a suitable control signal input from the incoming line to the vertical transmission track associated therewith. Electrical continuity exists in a transmission track of path routing arrangement l even if all transmission gates on the track -~
happen to be closed, thus, if such is the casel a control signal ~-input to the transmission track is nevertheless carried along the track and can be used to open a selected gate depending on ~
the character of the signal. Accordingly, for example, a ;
suitable control signal input from line Iolol in FIGURE 1, 2(a) or 2(b) to vertical transmission track Vl 1 could first travel along vertical transmission track Vl l to cause vertical transmission gate GV1 1 99 to open in response thereto, and r then continue along front horizontal transmission track Fl 99 to cause horizontal gate GHl 99 97 to open in response thereto.
v~ FIGURES 3 and 4 symbolically depict transmission gates . that open in response to suitable control signals carried by a transmission track. FIGURE 4 illustrates that portion of vertical r transmission track Vl 1 extending from vertical transmission gate GVl l 97 (not shown in FIGURE 1) to vertical transmission . .
`j gate GVl l 99 The view shown may be considered as a section taken along the centre line of track Vl l when looking at path routing arrangement l of FIGURE 1 from the front. The inner conductor 20 of track Vl l is thereby exposed to view as are end views of the inner conductors 20 of front horizontal transmission tracks Fl 97v Fl,98 and l,99 In the case of FIGURE 4, control signals to open a selected vertical gate are carried by vertical transmission 1~84183 ~
.
track Vl 1 Each vertical gate includes means responsive to open the gate if the control signal has the particular character to which the gate is designed to so respond. In FIGURE 4 the vertical gates are shown in their normally closed position - that is, there is no continuity between their gate contact line 24 -connected to inner conductor 20 of vertical transmission track Fl 1 and their gate contact line 25 connected to inner conductor 20 of the corresponding front horizontal transmission track Fl 97, Fl 98 or Fl 99, as the case may be. Thus in this condition, electrical signals are not able to pass from vertical transmission track Vl 1 to one of the front horizontal transmission tracks - shown.
~ Each vertical gate in FIGURE 4 is also shown to include :; , .
', a signal detection means or probe 86 which sehses the character ,~ of control signals that appear in vertical transmission track -~
~ Vl 1 In response to detection by the probe 86 of the appropriate 4~' ~ control signal for a given vertical gatef electrical continuity ;~ is formed between gate contact lines 24 and 25 of the particular ~j vertical gate. Then, the contact lines 24 and 25 of a particular ~
t~20 vertical gate, which contacts are symbolically spaced apart in `-FIGURE 4, can be thought of as symbolically joined to form a : .1 , .
direct electrical connect1on between inner conductor 20 of track Vl 1 and inner conductor 20 of the front horizontal transmission track corresponding to the particular vertical gate. Particular embodiments of transmission gates are discussed hereinafter.
For selectively opening any one of the 100 vertical transmission gates GVpqr (r=0,99) on a given vertical transmission track Vpq, it is necessary that each such gate be responsive to a control signal different from the control signals that open other ones of such gates. In other words, a control signal must be coded to open a particular vertical gate and the particular 1(3134183 gate must be coded to open in response to that particular cocled control signal.
~n the case of FIGUR~ 3, the control signals to open the horizontal gates are carried by the front horizon-tal trans-mission tracks assoeiated with the gates. Thus, for example, the eontrol signal to open horizontal gate G~I96 99 39 is earried by front horizontal transmission traek F96 99. Of course, this control signal will have gained access to traek F96 99 through - any one of the 100 vertlcal transmission gates GV96 q 99 (q=o, 0 99) interconnecting traek F96 99 with vertieal transmission traeks V96 q (q=0~99) on vertieal platform VP96.
Generally, the horizontal transmission gates are seleeted to open in the same manner as described for vertieal ; transmission gates. For seleetively opening any one of 100 horizontal transmission gates GHprS (s=0,99) on a given front horizontal transmission traek Fpr, it is necessary that eaeh such gate be eoded to open in response to a eoaed eontrol signal distinet from the eoded eontrol signals that open the other horizontal gates on the traek.
~o -Aecordingly, it will be eoneluded that to establish a desired eommunication link in the manner aforesaid, the eontrol signal input from an incoming line must be coded to open a partieular vertical gate and a partieular horizontal gate. One teehnique for eoding the control signal is to superimpose audio tones on predetermined control signal carrier rrequeneies, the tones being superimposed in a sequence representing the digits that iden-tify the outgoiny line with which it is desired to establish a communication link.
For purposes of illustration it will be assumed that 3 digits are represented by single frequency audio -tones as appears in Table B following:
- 2~ - :
1i~84183 TONE TONE
DIGITFREQ. (HZ) DIGIT FREQ. (HZ) 3 4600 8 5600 ;
TABLE B
The particular tones selected are so called "out-of-band" audio tones because, while they are within the audio range - i of frequencies, they are above the usual voice frequency range ;;~
j of many common telephone communications systems. --Tones to open vertical transmission gates will be superimposed on a 1 MHZ carrier frequency and tones to open hori- ~ -zontal transmission gates will be-superimposed on a 2 MHZ carrier . ", . , ' frequency. The selection of 1 MHZ and 2 MHZ carriers is made because these frequencies are outside the frequency range of the ~,l selected communications carriers (See Table A) and because the ~'`
l circuitry of the vertical and horizontal transmission gates can be 20 made much smaller in size than, for example, the circuitry that would be required to detect tones superimposed on the communication carriers which, as will be recalled, may occupy any one of ten channels together spanning a broad range of frequencies. Also,these frequencies are sufficiently high to avoid the generation of currents on the outer surface of the coaxial tracks causing interference. ~ ~-The selection of tone frequencies is somewhat arbitrar~.
The tones could, for example, lie in the voice frequency range rather than an out-of-band range and could, for example, comprise tones with two frequency components as are used in some common telephone systems. However, if voice frequency tones are used, additional care may be needed to ensure that the means providing the control signals to the path routing arrangement does not 1~84183 - behave in a manner such that undesirable false tones would be provided in response to voice frequency intelligence.
Referring now to FIGURE 1, 2(a~ or 2 (b), if, for example, the tones 5800 HZ and 5800 HZ appear in sequence (ie.
the digit sequence 9-9) superimposed on a 1 MHZ carrier frequency and then the tones 5800 HZ and 5400 HZ appear in sequence (ie.
the digit sequence 9-7) on a 2 MHZ carrier frequency, all of which appear as an input control signal from line Iolol to vertical transmission track Vl 1' then, the sequence 5800 HZ -5800 HZ
L0 -5800 HZ -5400 HZ (ie. 9-9-9-7) has identified outgoing line ~9997 If vertical transmission gate GVl 1 99 is coded to open in response to the digit sequence 9-9 on a 1 MHZ carrier and if horizontal transmission gate GHl 99 97 is coded to open in response to the digit sequence 9-7 on a 2 MHZ carrier, both gates will be open when the entire sequence 9-9-9-7 is completed and a link for carrier communications between incoming line Iolol and outgoing line ~9997 will thereby be established.
A circuit for a transmission gate which opens in response to suitable coded carrier signals appearing in a transmission track is shown in FIGURE 5. As will become apparent, the circuit also includes means to close the gate in response to suitable coded carrier signals appearing in the transmission track. Once having decided to use a transmission track to carry signals to open the gate it is considered that it would be preferable to also use means to close the gate in response to signals appearing in a transmission track. Of course, other means could be used.
Since the basic structure of every vertical and hori-zontal transmission track may be basically the same, TRACK 1 of FIGURE 5 may be considered as a vertical transmission track with TRACK 2 being a front horizontal transmission track, or, TRACK 1 1C~8~18~
may be considered as a front horizontal transmission track with TRACK 2 being a cross horizontal transmission track. If TRACK 1 is considered as a vertical transmission track, then code receiver 89 is tuned to receive 1 MHZ carrier frequencies as an input on line 88 from sensing coil 87 which detects signals on gate contact line 24. Similarly, if TRACK 2 is a front horizontal transmission F
track, then code receiver 89 is tuned to receive 2 MHZ carrier '',;' frequencies. In either case, the output of code receiver 89 on line 90 (which also appears on lines 94 and 95) is simply the ;~ 10 audio tone that is superimposed on the carrier.
The design of receivers such as code receiver 89 which received a modulated carrier frequency input signal and produce as an output the modulating frequency is very well known in the art and will not be discussed in detail. The same is true of many other circuit elements which will be referred to hereinafter with ~ -reference to FIGURE 5 and other FIGURES. These elements include receiver detectors (R/D) which receive an ac input and produce a dc logic signal as an output if the input frequency is the fre-quency or frequency range for which the receiver is tuned; flip-flops; multivibrators; and other common circuit elements.
Referring again to FIGURE 5, the normal condition of the circuit is that normally open switch SWl between gate contact lines 24 and 25 is open as shown. Thus the transmission gate as a whole is normally closed and does not permit electrical signals to pass between TRACK 1 and TRACK 2. Switch SWl remains open so long as the control signal input on line 100 to the switch control SWC, which control mechanically drives switch SWl, remains at logical 0. If such control signal input goes to logical 1, switch control SWC closes switch SW
making electrical contact between gate contact lines 24 and 25 and therefore between line 20 of TRACK 1 and line 20 of TRACK 2. The transmission gate is then open.
Detail "A" of FIGURE 5 illustrates a basic circuit to energize a relay coil C of switch control SWC to cause switch SWl to close. A logical 1 input to the base of transistor Ql causes transistor Ql to turn on. When transistor Ql is on, the , bias across resistor Rl produced by the voltage divider action of resistors Rl and R2 biases transistor Q2 on allowing current to flow from voltage source V+ through coil C energizing the L0 coil. The bottom plate P of switch SWl is then magnetically drawn towards coil C against the action of spring S attached to the plate P and the frame F of switch control SWC. When the input on line 100 goes to logical 0, transistors Ql and Q2 are off and the coil C is de-energized. Diode D suppresses inductive switching spikes on turn-off.
As can be seen in FIGURE 5, the circuit of the trans-mission gate includes three flip-flops FFl, FF2 and FF3. These -~
flip-flops are of the edge triggered set-reset variety each having a set input Sl, S2 or S3 as the case may be, a reset ~ input Rl, R2 or R3 as the case may be, and a set output Pl, P2 or P3 as the case may be. The logical state of a-set output depends on whether the flip-flop last received a set command on its set input or a reset command on its reset input. Herein, it is assumed that all set-reset flip-flops are so designed that a set or reset command, as the case may be, is a switching transition from logical 0 to logical 1.
The normal logical state of set outputs Pl, P2 and P3 of flip-flops FFl, FF2 and FF3 respectively is logical 0. As can be seen, the output P3 of flip-flop FF3 on line 99 is also 3~ one input of dual input logical "AND" gate ANDl. Thus, regardless 1~D84183 of the logical state of the other input to gate ANDl on line ~
100, switch SWl will be logical 0 of output P3 of flip-flop .
~F3 is logical 0.
The normal condition of switches SW2 and SW3 appearing in FIGURE 5 is also open. That is, when the input to switch SW2 from output Pl of flip-flop FFl on line 93 is logical 0, switch SW2 is open; when such input is logical 1, the switch ~`
~ is closed. Likewise, when the input to SW3 from output P2 - of flip-flop FF2 via lines 98 and 105 is logical 0, switch SW
is open; when such input is logical 1, the switch is closed.
The circuit of FIGURE 5 includes three receiver detectors R/Dl, R/D2, and R/D3, the first of which is for detecting the first audio tone of the two tones required to identify the gate, the second of which is for detecting the second audio tone of the two tones required to identify the gate, and - the third of which is for detecting a DISCONNECT tone to cause the transmission gate to be closed. In this case, it will be assumed that a disconnect tone is a 6000 HZ out-of-band tone.
When the proper tone frequency is on line 90 at the input of receiver detector R/Dl, on line 96 at the input of receiver detector R/D2, or on line 106 at the input of receiver detector R/D3, as the case may be, the output of the receiver detector is logical 1 - otherwise it is logical 0. Thus, for example, if the transmission gate is coded to detect the tone sequence 4600 HZ - 5400 HZ (ie. the digit sequence 3-7), receiver detector R/D~ is tuned to receive and detect a 4600 HZ tone and receiver detector R/D2 is tuned to receive and detect a 5400 HZ
tone. Receiver detector R/D3 is tuned to receive and detect a 6000 HZ tone. In each case it is assumed that all tones initially appear on the carrier frequency (1 MHZ or 2 MHZ, as the case may be) that code receiver 89 is tuned to receive.
1~84~8~
As will be seen, the receiver detectors RJDl to R/D3 and other receiver detectors referred to herein are used to ~ -' control the switching of flip-flops and in some cases to trigger ' one-shot multivibrators. Depending on the design of a receiver ' detector per se, the logical transition at its output in response to the beginning of or end of an ac signal at its input may not be sufficiently fast to cause switching or triggering of a fol-lowing flip-flop or multivibrator, as the case may be. Also, there may be undesirable ripple at the output of a receiver detector.
Accordingly, it may then be necessary to insert a threshold device (not shown) such as a Schmitt trigger at the output of ~;
the receiver detector.
To assist in describing the circuit shown in FI~URE 5, reference will be made to FIGURE 6 which shows typical waveforms at various points of the circuit. The DISCONNECT tone in FIGURE 6 is shown with dashed lines because the waveforms are ! indended to indicate response both with (solid lines) a DISCONNECT tone.
When the 4600 HZ first digit appears on line 90 at ~0 the input of receiver detector R/Dl, the output on line 91 to the input of logical inverter INVl goes to logical 1 as shown~
in FIGURE 6. The output of inverter INV3 on line 92 to input Sl of flip-flop FFl goes to logical 0, but since this is a negative going transition from logical 1 to logical 0 there is no response by flip-flop FFl. However, when the 4600 HZ tone terminates, the output of receiver detector R/Dl on line 31 returns to logical 0 and the output of inverter INV3 on line 92 returns to logical 1. Accordingly, there is a set command at the input Sl of flip-flop FFl and its output Pl on line 93 ,0 goes to logical 1 causing switch SW2 to close.
~084183 :~?
When the 5400 HZ second digit tone appears on line 96 at the input of receiver detector R/D2 (via lines 90, 94, 95 and switch SW3 which switch is now closed), the output on line !7",/ 97 to input S2 of flip-flop FF2 goes to logical 1. Such trans-.. ~ ition at the input S2 of flip-flop FF2 is a set command to flip-: . , flop FF2 and its output P2 on lines 98 and 105 goes to logical 1.
, It might be noted that there is no inverter between 'i .
the output of receiver detector R/D2 and the input S2 of flip-flop FF2 corresponding to inverter INV3 between the output of receiver detector R/Dl and input Sl of flip-flop FFl. Inverter INV3 performs a delay timing function that prevents switch - SW3 from closing before the first digit tone terminates. In this particular example where receiver detector R/D2 is tuned to a different frequency (5400 HZ) than the frequency (4600 HZ) to which receiver detector R/Dl is tuned, such a delay is not ~;
necessary and the output of R/Dl could be taken directly to the input Sl of flip-flop FFl. Switch SW2 would then close at the beginning of the 4600 HZ tone. This tone would then appear on :
line 96 at the input of receiver detector R/D2, but since R/D2 is not tuned to 4600 HZ, it would not respond. However, if the first and second digits that identified a transmission gate happened to be the same - for example 3-3 instead of 3-7 as in . the present case, then both flip-flops FFl and FF2 would be set :~ by the first tone because receiver detector R/D2 would respond.
Returning again to the sequence of operation, when the output P2 of flip-flop FF2 goes to logical 1, a set command is provided on line 98 to set input S3 of flip-flop FF3. Thus, as shown in FIGURE 6, the output P3 of flip-flop FF3 on line 99 goes to logical 1. If, as may occur, the output P3 of flip-flop FF3 was already at logical 1 then there would of course be no 1~8418~
change. Also, as shown in FIGURE 6 by the continuing solid line of the waveform for line 99, the output on line 99 remains at logical 1 so long as no DISCONNECT tone arrives. Assuming for the moment that the input on line 108 to gate AND1 is logical 1, the logical 1 condition on line 99 appears on line 100 causing switch SWl to close. The transmission gate is now open.
When the output P2 of flip-flop FF2 goes to logical 1, the output appears on line 105 via line 98 causing switch SW3 ;~
to close. If a 6000 HZ DISCONNECT tone then appears on line 90, it reaches the input of receiver detector R/D3 via line 94 and switch SW3 causing the output of R/D3 on line 107 to go to logical 1. This transition is received on line 107 as a reset command to reset input R3 of flip-flop FF3 which causes the output P3 of flip-flop FF3 on line 99 to go to logical 0 (shown by dashed lines for line 99 in FIGURE 6). This output also appears through gate ANDl on line 100 as the input to switch control SWC. Since switch SWl is open for a logical 0 input, the transmission gate will now be closed.
In summary, to open the transmission gate it is necessary to provide the tones 4600 HZ - 5400 HZ in sequence.
To close the gate it is necessary to provide the tones 4600 HZ - 5400 HZ - 6000 HZ in sequence. Nothing has yet been said about the timing of tones in the sequences.
To enable the transmission gate to detect recurring sequences of the tones 4600 HZ and 5400 HZ, a timing circuit is included which causes flip-flops FFl and FF2 to be reset a pre-determined time after the first tone (4600 HZ) of the sequence is detected. The basic elements of the timing circuit as shown in FIGURE 5 are one-shot multivibrator O/Sl and logical inverter INV4. It is assumed that one-short multivibrator O/Sl produces ~ lG84183 a Iogical 1 pulse having a predetermined pulse width in respon , ` !
s: to a negative going logical transition (logical 1 to logical 0) appearing at its input on line 101. The input on line 101 is also the output of inverter INV3 on line 92. The output of 0/S
is on line 102 to the input of inverter INV4, the output of which inverter on line 103 is also the input on line 104 to reset :~
inputs Rl, R2 of flip-flops FFl, FF2 respectively.
As will be seen, the effect of the timing circuit is that the se~uence of tones required to open or close the o transmissiOn gate must be completed within the duration of the logical 1 pulse of one shot multivibrator 0/Sl. Typically, the duration of a tone may be of the order of 50 milliseconds and tones may be spaced 50 milliseconds apart, thus, if the one-shot multivibrator is triggered when the first digit tone is first detected (as the circuit shown in FIGURE 5 is designed to do) rather than on termination of the first digit tone (as the circuit of FIGURE 5 could obviously be modified to do), a pulse duration of 250 milliseconds would suffice for the circuit of FIGURE 5 and leave a margin for timing fluctuations.
The operation of the timing circuit is as follows and again reference may be made to FIGURE 6. When the output of ~ !
inverter INV3 appearing on line 101 via line 92 goes from logical 1 to logical 0, one shot-multivibrator 0/Sl is triggered producing at its output on line 102 a logical 1 pulse as shown in FIGURE 6. The pulse width shown is somewhat greater in duration than need be and could terminate any time after the condition on line 99 as shown in FIGURE 6 goes to logical 0.
Since the output of INV4 on line 103 is the logical inverse of the condition on line 102, a logical 0 pulse appears on line 103. When the logical 0 pulse terminates a reset command 1~4183 is provided on line 104 from line 103 to the reset inputs Rl, R2 of flip-flops FFl, FF2 respectively. Accordingly, the outputs Pl, P2 of flip-flops FFl, FF2 respectively go to logical 0 as shown in FIGURE 6 and switches SW2, SW3 are opened.
A further characteristic of the transmission gate that results from use of the timing circuit is that if the required first digit tone does appear, but is followed by a second digit tone other than the required second digit tone, flip-flop FFl will only be set for the duration of the output pulse of one-shop multivibrator O/Sl.
It is preferable that some means be included to prevent the opening of a transmission gate under certain circumstances.
In FIGURE 5 busy circuit 110 is a means which prevents the closure of switch SWl if the condition on line 99 goes to logical 1 when an input to busy circuit 110 on BUSY LINE 109 is logical 1.
Busy circuit 110 includes buffer amplifier BUFFl, two logical inverters INVl and INV2 and field effect transistor FETl. When the condition on line 100 is logical 0, the output of inverter INV2 is logical 1 which closes FETl whereby the logical condition on BUSY LINE 109 becomes the input to inverter INVl. Unless the condition on line 109 is forced to logical 1 by an external source applied as an input to the line, the logical condition on the line will be logical 0. The output of inverter INVl on , line 108 will thus be logical 1. If the condition on line 109 is forced to logical 1, the output of INVl on line 108 will be logical 0 which in effect disables gate ANDl such that switch SWl cannot be closed even if the proper sequence of tones are received by the transmission gate.
If there is no disabling busy condition and line 100 does go to logical 1, FETl will be open because the input thereto -` -` 1884183 from inverter INV2 will be logical 0. The input to inverter INVl will be logical 0 independent of the condition on line 109, thus the condition on line 108 at the output of inverter INV
will be logical 1 (as is required to have the logical 1 condition at the output of gate AND1 on line 100). Through buffer amplifier BUFF1, the condition on line 109 becomes logical 1 which condition may become the "external source" referred to just previously except that it is the external source for corresponding BUSY LINES 109 of selected other transmission gates to which BUSY ~INE 109 of the particular transmission gate shown in FIGURE S is connected. ~ ;-As will be seen, it is contemplated that in some embodi-ments of the path routing arrangement 1, the selective closing of transmission gates may require that a transmission gate be ; completely identified on its particular platform. Two tone identification as just discussed merely identifies a front i;
horizontal transmission track on a given vertical platform. `
For example, the tone sequence 4600 HZ - 5400 HZ (digit sequence 3-7) may identify vertical transmission gate GVl 1 37 ~ that is, the 37th vertical transmission gate of vertical track Vl 1 on vertical platform VPl. However, this tone sequence also identifies 99 other vertical transmission gates GVl q 37 (q=0,2,3..,99) on the 99 other vertical transmission tracks Vl q (q=0,2,3,...,99) connecting to the same front horizontal transmission track Fl 99 on the same vertical platform VPl. To completely identify a vertical transmission gate on a given vertical platform (on which there are 10,000 gates), and assuming that tone sequences are used generally as aforesaid, then, a sequence of four tones will be sufficient. For example, the first two tones may identify the transmission gate for a given vertical transmission ~84183 track, the last two tones may identify the transmission track itself (which track, for a given vertical platform, is identified by the last two digits of the number that identifies the associated incoming line).
As shown in FIGURE 5(a), the circuit shown in FIGURE 5 may readily be modified to detect a sequence of more than two tones. FIGURE 5(a) repeats (with addition of a logical inverter INV5) the portion of FIGURE 5 that detects the second tone of a sequence (indicated in FIGURE 5(a) as STAGE 2) and the portion of FIGURE 5 that detects a DISCONNECT tone on completion of a proper preceding sequence of tones. Elements of FIGURE 5(a) corresponding to elements of FIGURE 5 have been identified by the same characters. FIGURE 5(a) shows in addition STAGES 3...N
which stages are identical in structure to STAGE 2 and respond in the same manner as STAGE 2 except that their respective receiver detectors are tuned to respond to audio tones (ie. Table B tones) that may be different than the audio tone to which STAGE 2 responds.
Thus, for example, when the output of flip-flop FF2 appearing at terminal y of STAGE 2 in FIGURE 5(a) is logical 1 (which by reason of INV5, occurs at the termination of a tone detected by receiver detector R/D2), the switch in STAGE 3 corresponding to switch SW2 in STAGE 2 will be closed by such logical 1 output when it appears on line 93-3 at terminal x of STAGE 3. A proper tone appearing on line 95-3 at terminal u of STAGE 3 will, when it terminates, cause to be set the flip-flop in STAGE 3 corresponding to flip-flop FF2 in STAGE 2.
The output of STAGE 3 at terminal y will then be logical 1 and the next stage, if any, will then be conditioned to detect the next proper tone of the sequence. Of course, if four tones are to be detected, then four stages (N=4) are required.
1~84~3 The output at terminal y of the last stage. STAGE N, provides the set command on line 98 to flip-flop FF3. As can be inferred from FIGURE 5(a), the reset inputs of the flip-flops in STAGES 2 to N are connected by a cbmmon line 104, thus, the flip-flop of all stages are reset simultaneously by a logical 0 to logical 1 transition on line 103. One shot multivibrator 0/Sl (not shown in FIGURE 5(a)) must of course have a pulse width sufficiently broad to ensure that complete sequences of tones can be detected.
Thus, for example, and assuming that the tones identi-fying the front horizontal track precede the tones identifying the vertical transmission track, then, the required sequence of tones to open vertical transmission gate GVl 1 37 would be 4600 HZ - 5400 HZ - 4000 HZ - 4200 HZ (digit sequence 3-7-0-1).
To close the gate would require the same sequence followed by a :
6000 HZ DISCONNECT tone.
FIGURE 7 illustrates a more basic transmission gate circuit which does not incorporate a timing circuit and does not require a DISCONNECT tone to be first preceded by the two-tone sequence required to open the gate. Only a portion of the circuit has been shown but it may be thought of as replacing all circuitry in FIGURE 5 between the output of code receiver 89 and the line 99 input to gate ANDl in FIGURE 5. As can be seen, what is shown in FIGURE 7 includes many of the same elements as shown in FIGURE 5 interconnected in a very similar manner as in FIGURE 5, but excludes many other elements. One additional element, inverter INV6 is included.
The sequential operation of flip-flops FFl and FF2 in FIGURE 7 to cause a logical 1 condition to appear on line 99 at the output P2 of flip-flop FF2 is identical to the sequential ~ 84~.83 :
operation of flip-flops FFl and FF2 in FIGURE 5 to cause a logical 1 condition to appear on line 98 in FIGURE 5. However, flip-flops FFl and FF2 in FIGURE 7 are not automatically reset within a predetermined time after the proper first digit tone is detected by receiver-detector R/Dl in FIGURE 7. Instead, they are reset directly by receiver detector R/D3 when it receives at its input on line 94 a disconnect tone and in response produces at its output on line 114 a logical 1 condition which is the input to inverter INV6. The output of INV6 on line 115 then goes to logical 0. When the disconnect tone terminates, the output of INV6 on line 115 returns to logical 1. The transition from log-ical O to logical 1 on line 115 appears as a reset command to re-set inputs Rl, R2 of flip-flops FFl, FF2 respectively. Since a switch does not appear before the input of receiver detector R/D3 (contrary; to the case in the circuit of FIGURE 5), a reset command will result whenever a disconnect tone appears on line 90 at the output of code receiver 89. The reason that the circuit is designed to reset flip-flop FF2 at the termination of a disconnect tone rather than the beginning is that the disconnect tone will ordinarily cause closure of two transmission gates -one vertical transmission gate and one horizontal transmission gate - it being superimposed on both a 1 MHZ and 2 MHZ carrier.
If the external sources are controlled such that the carriers only enter on the incoming line (they could enter from an out-going line after a communication link was established) and assuming that the disconnect tone is simultaneously imposed on both the 1 MHZ carrier and the 2 MHZ carrier, then the possibi-lity exists that thevertical gate will close before the hori-zontal gate can respond if the vertical gate closes at the beginning of the disconnect tone.
A variety of circuit structures to effect theopening and closing of gates by use control signal inputs from the ~841B3 transmission path are possible and will occur to those skilled in the art. As will be seen, a particular structure may possess characteristics which impose practical limitations on the use to which the path routing arrangement in which the circuits are used is put depending on line or terminal equipment in associa-tion with which the path routing arrangement is used. Likewise, the transmission gates could be designed to respond to code signals other than the particular code signals selected. In the circuits represented by FIGURES 5 and 7, two audio tones in proper sequence are required to identify the transmission gate.
Theoretically one tone could be used to identify a particular transmission gate, but in a path routing arrangement where 100 transmission gates appear on a transmission track, 100 separate tones would have to be used if only one carrier frequency was used to carry code tones for transmission gates on that track. However, it would be possible to use different carrier frequencies for different groups of gates on the same transmission track and at the same time use ten or some other number of superimposed tones on those carrier frequencies. For example, for a transmission track providing control signals to 100 transmission gates, one of twenty tones on one of five carriers would be sufficient to uniquely identify each trans-mission gate on the particular track. Of course, this would not uniquely identify a gate on a platform having 100 tracks. In theory, it would be possible to use unmodulated carriers coded by selection of carrier frequency. For example, 1.0 MHZ might represent the digit 0, 1.1 MHZ the digit 1, 1.2 MHZ the digit 2, and so on.
All the foregoing is predicated by the comment made earlier that the control signals for transmission gates need not be carried by the transmission tracks. For example, switch SWl 1~84~83 ln FIGURE 5 could be controlled by purely digital means responsive to serial or parallel logic control signals (or a combination of serial and parallel logic control signals, which means would receive its logic inputs from circuit lines other than the transmission tracks. The techniques to open a switch by a circuit that is selectively responsive to one of many possible digital logic input combinations appearing on one (ie. completely serial logic) or more input lines are well known and need not be discussed in any detail. The logic signal 0 inputs may, for example be binary, or binary coded decimal or some other digital code. If the particular logic signal inputs happen to be the matching combination for which the transmission gate circuit is coded, then the gate clos~s.
The use of transmission gates having the circuit structures shown in FIGURES 5 and 7 will now be described with reference to path routing arrangement 1 of FIGURE 1.
Where the path routing arrangement 1 incorporates transmission gates such as that shown in FIGURE 7, it is preferable to ensure that once a bi-directional link is established o between any given ingoing line and any given outcoming line that no signal from any other incoming line be allowed access to any transmission track of the bi-directional link. The reason is that unless some means external to the path routing arrange-ment is used to prevent a DISCONNECT tone from entering on a second, third, etc. incoming line, the link may be prematurely terminated. A 6000 HZ tone will cause closure of any gate, the code receiver of which is tuned to the 1 MHZ or 2 MHZ carrier, as the case may be. If some such external means is included, then the subsequent incoming line from which access was gained will continue to have access after it would otherwise have pro-1~84183 vided a DISCONNECT tone and until a DISCONNECT tone is forth-coming from another source.
To deny access to signals from incoming lines other than the incoming line which forms part of the link, requires the disabling of all vertical transmission gates which connect to the front horizontal track of the link, and of all horizontal transmission gates which connect to the cross horizontal track of the link (other than the one vertical transmission gate and one horizontal transmission gate that are part of the link).
Assume, for example, that in FIGURE 1 a communication link has been established between incoming line lolol and out-going line ~9997. Then, vertical transmission gate GVl,l,gg and horizontal transmission gate GHl 99 97 are open. The gates which are to be disabled are horizontal transmission gates GHp 99 97 (p = 0,2,3, .... 99) and vertical transmission gates -~
GVl 99 (q = 0, 2, 3, ..... .99). If the transmission gate structure shown in FIGURE 7 is used for the vertical and hori-zontal transmission gates, and assuming the BUSY CIRCUIT 110 of - FIGURE 5 is incorporated, then the desired disabling function is achieved if BUSY LINE 109 of each horizontal gate GHp 99 97 (p = 0,99) is connected to the BUSY LINE 109 of every other horizontal gate GHp 99 97 (p = 0,99) and if the BUSY LINE 109 of each vertical gate GVl q 99 (q = 0,99) is connected to the BUSY LINE 109 of every other vertical gate GVl q 99 (q = 0,99).
When transmission gates of path routing arrangement 1 are dis-abled in the manner just described, it becomes evident that when a transmission path is established and in use, only two of the assumed 20 possible communication channels may be occupied in the transmission path (see Table A). As will become apparent, this is a somewhat inefficient use of the path routing arrange-ment.
.
..
1~841~33 It will be appreciated that a significant amount of potential blockage is present in the embodiment just considered.
For the particular example, no other incoming line to vertical platform VPl of FIGURE 1 can gain access to any outgoing line of horizontal platform HPg9, including outgoing line ~9997 which was the outgoing line in use. The reason is that incoming lines to vertical platform VPl can only gain access to horizontal platform HP99 by way of front horizontal transmission track Fl 99 through vertical gates GVl q 99 (q = 0 99) If transmission gates such as the transmission gate shown in FIGURE 5 are used for horizontal transmission gates; -and, transmission gates such as the transmission gate shown in FIGURE 5(a) having four STAGES (i.e. N=4) are used for vertical transmission gates, then, the amount of blockage can be reduced.
It is implicit that reduction in blockage requires that any given front horizontal transmission path may form part of more than one bi-directional communication link at one time.
Hence the task is now to ensure that the same channel is not occupied in more than one bi-directional link. This requires ~0 knowledge of the channels that will be occupied during any given bi-directional link. There are various ways in which the channels that will be occupied can be predetermined depending on the characteristics of equipment external to the path routing arrangement connecting to the incoming and outgoing lines.
One way to assign channels is to require that a communication signal from a given incoming line to any desired outgoing line always be in a channel determined by the identifi-cation of the incoming line and that a communication signal back from the desired outgoing line to the given incoming line always be in a channel determined by the identification of the outgoing 11~84~83 line. Alternately channels may be assigned by requiring that the communication signals from a given incoming line to any desired outgoing line and from the desired outgoing line to the `
given incoming line be in separate channels both of which are determined by the identification of the incoming line.
In the following discussion, it is assumed that the channel for a communication carrier from an incoming line is assigned depending on the last digit of the number identifying the incoming line. Thus, for example, communication signals from incoming line lolol to path routing arrangement 1 of FIGURE 1 are conditioned in advance to occupy channel 1 LOW - the carrier frequency being 100 MH~ (see Table A). Likewise, for example, communication signals from outgoing line ~9997 to path routing arrangement 1 are conditioned in advance to occupy channel 7 HIGH - the carrier frequency being 260 MH~ (see Table A). If a bi-directional link is established between line lolol and line , channel 1 LOW and channel 7 HIGH are occupied on front horizontal transmission track Fl 99. Hence it is necessary to deny access to track Fl 99 from any other incoming line from which signals occupying channel 1 LOW would arrive. On vertical platform VPl, signals arriving from incoming lines l (x = 0,9) would occupy channel 1 LOW, thus, for this example, it is necessary to deny access to incoming lines lolXl (x = ~`
0,2,3, ..., 9). Using the transmission gate of FIGURE 5, this result is achieved if the BUSY LINE 109 of each vertical trans-mission gate GVl xl 99 (x = 0,9) is connected to the BUSY LINE
109 of every other vertical transmission gate GVl,Xl,gg (x = 0,9).
Likewise, it is necessary to deny access to track ; Fl 99 from any outgoing line other than line ~9997 from which signals occupying channel 7 HIGH would arrive. On horizontal ., .
~34~83 platform HPg9, signals arriving from outgoing line ~99y7 (y = 0,9) would occupy channel 7 HIGH thus, for this example, -it is necessary to deny access to outgoing lines ~99y7 (y = 0,8).
Using the transmission gate of FIGURE 5(a), this result is achieved if the BUSY LINE 109 (not shown in FIGURE 5(a), of each horizontal transmission gate GHl 99 y7 (y = 0-9) is connected to the BUSY LINE 109 of every other horizontal transmission gate GHl 99 y7 (y = 0,9). At the same time all access to outgoing : line ~9997 through front horizontal transmission tracks other than front horizontal transmission track Fl 99 is denied by the connection of the BUSY LINE 109 of each horizontal transmission gate GHp,gg,g7 (p = 0,99) to the BUSY LINE 109 of every other horizontal transmission gate GHp 99 97 (p = 0,99).
Of course, the same BUSY LINE connections are made, mutatis mutandis, throughout path routing arrangement 1.
If all vertical transmission gates were merely identified by two tones, then, on a control signal sequence to close a given vertical transmission gate on a given front hor-izontal transmission track, all other open vertical transmission gates on the same front horizontal transmission track would close since such other vertical transmission gates are coded for the same two tones. To avoid such undesirable response, it is nec-essary to code the vertical transmission gates on a given front horizontal transmission track not only in respect of the front horizontal transmission track with which they are associated, but also in respect of the incoming line from which the control sig-nals are received. As has been said, on a given vertical plat-form, a vertical transmission gate is completely identified if it is identified by the last two digits of the number which identifies the incoming line from which the gate received control signals .~
'',' 1~84183 and by the last two digits ~f the number which identifies the front horizontal track to which the gate connects ~a leading 0 being added to this last number if necessary - for example, for front horizontal transmission track F21 8' (not shown in FIGURE 1), the last two digits are to be taken as 08 and not 18).
The operation of path routing arrangement 1 of FIGURE 1 using transmission gates as shown in FIGURE 5 for horizontal transmission gates and transmission gates as shown in FIGURE 5(a) for vertical transmission gates will now be considered by way of example. Firstly, the establishment of a bi-directional link between incoming line Iolol and outgoing line ~ggg7 will be con-sidered.
To give itself access to front horizontal transmission track Fl 99, incoming line Iolol must provide within the proper time interval the control signal sequence 5800 HZ - 5800 HZ
4000 HZ - 4200 HZ (digit sequence 9-9-0~1) on a 1 MHZ carrier.
If vertical transmission gate GVl 1 99 is not disabled by a busy signal on its BUSY LINE-109, then gate GVl 1 99 will open in response to such sequence. Control signals from incoming line Iolol may now travel down front horizontal transmission track Fl~gg~ ' :
; '~o give access to cross horizontal transmission track Cg9 97 from track Fl 99, incoming line Iolol must now provide within the proper time interval the control signal sequence 5800 HZ - 5400 HZ (representing the digit sequence 9-7) on a 2 MHZ carrier. If horizontal transmission gate GHl 99 97 is not disabled by a busy signal or its BUSY LINE 109, then gate GHl 99 97 will open in response to the sequence. Access would then be gained to cross horizontal transmission track Cgg 97 and 30 necessarily to outgoing line ~9997 through slot Sg9 97 and back horizontal transmission track B99 97. Outgoing line ~9997 would have access to incoming line 10101in the opposite direction over the now established path.
If horizontal transmission gate GHl 99 97 had been disabled by a busy signal on its BUSY LINE 109, the access gained to front horizontal transmission track may be terminated if line lolol provides within the proper time interval the control sig-nal sequence 5800 HZ - 5800 HZ - 4000 HZ- 4200 HZ - 6000 HZ
(representing the digit sequence 9-9-0-1 followed by the DIscoNNEcTtone) on a 1 MHZ carrier. The non-establishment of such access might be determined by external equipment (not shown in FIGURE 1) assoclated with incoming line lolol by thenon-receipt of a signal from line ~9997indicating that access had been established.
The non-establishment of access to front horizontal transmission track Fl ggcould be determined in a similar manner.
If a complete bi-directional link between lines lolol and ~9997 is established, it may be terminated by proper control signals within the proper time interval from either the incoming line or the outgoing line or both. If the control signals are to be provided from incoming line lolol the complete sequence 5800 HZ - 5400 HZ - 6000 HZ (9-7-DISCONNECT) on a 2 MHZ carrier to close horizontal gate GHl 99 gj; then 5800 HZ - 5800 HZ -4000 HZ - 4200 HZ - 6000 HZ (9-9-0-1-DISCONNECT) on a 1 MHZ
carrier to close vertical- gate GVl 1 99- The vertical gate must not be closed before the horizontal gate. If the control sig-nals are to be provided from outgoing line ~9997 the complete sequence is 5800 HZ -5800 HZ - 4200 HZ - 6000 HZ (9-9-0-1-DISCON-NECT) on a 1 MHZ carrier to close vertical gate GVl 1 99, then 5800 HZ - 5400 HZ - 6000 HZ - (9-7-DISCONNECT) on a 2 MHZ carrier to close horizontal gate GHl,gg 97. In this instance,the horizontal . ~ , ' . ~
1~84183 :.
gate must not be closed before the vertical gate. If -the control signals are provided from both lines, then of course the sequence of gate closure is not crucial.
It will now be assumed that a bi-directional link between incoming line Iolol and outgoing line ~99~7 has been established. Channel 1 LOW from line Iolol to line 09997 is occupied and channel 7 HIGH from line ~9997 to line Iglol is occupied. No incoming line to vertical platform VPl in FIGURE
1 having as a last dig~t identification the number "1" can gain access to horizontal transmission track ~1 99 Likewise, no incoming line to vertical platform VPl that has as a last digit identification a number other than "l",an~ which does again access to track Fl 99, can gain access to any cross horizontal trans-mission track having as a last digit identification the number "7" (except, as will be discussed track ~99 97 associated with outgoing line ~9997). Front horizontal transmission track Fl 99 can still be used in a bi-directional link between an incoming line having a last digit identification other than "1" and an outgoing line having a last digit identification ,j~20 other than "7". If a second bi-directional link is established subject to these conditions, then, similar conditions apply for ;~ a third link, a fourth link, and up to ten links for the twenty channels assumed. If ten links are formed then the last digit identification of each of the ten incoming lines will differ - from each other, and the last digit identification of each of the ten outgoing lines will differ from each other. For example, front horizontal transmission track Fl 99 might form part of the bi-directional link between the following pairs of lines at the same time:
. .
;LINE``~AI~g ~ CHA~æ~S;~q 0101 ~9997 1 LOW - 7 HIGH
(2) I - ~ 2 LOW - 8 HIGH
(3) I0173 ~9939 3 LOW - 9 HIGH
(4) I0104 ~9940 4 LOW - 0 HIGH
(5~ I0185 ~9951 5 LOW - 1 HIGH
(6) I - ~ 82 6 LOW - 2 HIGH
~7) Iol47 ~9903 7 LOW - 3 HIGH
(8) I - ~ s~ LOW - 4 HIGH
10(9) I - ~ 9 LOW - 5 HIGH
(10) I - ~ O LOW - 6 HIGH
, ,~
TABLE C
- It will be appreclated that the concurrent presence of more than one bi-directional link through a given front ~ :
: horizontal transmission tracX will mean that an incoming line~or : an outgoing line will necessarily receive from the path routing arrangement all channels from the other incoming and outgoing ` lines which lines connect through the same front horizontal transmission track. For example, referring to TABLE C, incoming .. :~
~ 20 line Iolol would not only receive channel 7 HIGH from outgoing `.
`:s~ line ~9997 but also would receive channels 0 to 6 and 8 HIGH
. from the other outgoing lines and would receive channels 0, and :: . r~
2-9 LOW from the other incoming lines because paths would be .'' defined from one incoming line to others. For example, the path between incoming line Iol22 (see TABLE C) and incoming line Iolol would be defined by vertical transmission track Vl 22 (not shown);.the portion of front horizontal transmission '; .
J track ~1 gg between vertical gate GVl 22 g9(not shown) and ~ :
vertical gate GVl 1 99; and vertical transmission track Vl 1 ``
. 30 It is contemplated that the external equipment (not shown) that .
. ' "~ ;:
-44- ` ~
:~ .
1 .
1{~84183 may receive multiple channels from incominy and outgoing lines -~
ill include means to discriminate signals on a particular channel and heavily attenuate signals on other channels -which it does no-t desire to receive.
There is a situation which has not been considered and that is where, for example, there is a bi-directional link between incoming line Iolol and outgoing line 09997 and an attempt is made to establish a bi-directional link between some other incoming line and outgoing line 09997 using front , 10 horizontal transmission track Fl 99. Say, for example $hat the attempted link was between incoming line Iol25 (not shown) `-and outgoing line 09997. Incoming line Iol25 would first provide the control signal sequence 5800 HZ - ~800 HZ - 4400 HZ -5000 HZ (digit sequence 9-9-2-5) on a 1 MHZ carrier the~eby giving access to track Fl 99 through vertical transmission track Vl 25 and vertical transmission gate GVl 25 99 and would then
5! ' ' ' provide the digit sequence 5800 HZ - 5400 HZ (digit sequence ~; :"
9-7) on a 2 MHZ carrier, prospectively to open horizontal gate GHl 99 97. However, horizontal gate GHl 99 97 would already `
be open. It would not close in the absence of the required ~'~ 6000 HZ DISCONNECT tone. However, a transmission path would -` 'd ~ :
i exist between incoming line Iol25 and outgoing line 09997. 1 ~
. ~.
j- If the external equipment (not shown) to which line 09997 is connected is conditioned to recelve channel 1 LOW
i:'.'5 from line Iolol, attempted communications on channel 5 LOW
.. i; . .
`~i from line Iol25 would be heavily attenuated and would not .-J
interfere. However, the external equipment (not shown) to-which line Io125 is connected would presumably be conditioned ; to receive channel 7 HIGH from line ~9997 and would accordingly '` 30 receive communication intended to be directed only to line I
.. . . . .. . . . .. .
1~84183 Thus, it is preferable that the external equipment (not shown) associated with line ~9997 include means to detect the instance of access by line Iol25 and to send a signal back through the path routing arrangement to disable reception by the external equipment (not shown) associated with line I
of channel 7 HIGH.
This characteristic of unwanted access to other communications may be avoided by assigning channels in complete dependency on the last digit of the identifying number of the line. For example, channel numbers from an incoming line to path routing arrangement 1 as set forth in Table A may be fixed as indicated, but channel numbers from an outgoing line to path routing arrangement 1 would be variable depending on the channel number of the incoming line and not fixed depending on the last digit of the number identifying the outgoing line.
Thus, for example, incoming lines having as a last digit identi-fying the line the number N (ie. IwxyN) would provide communication s1gnals to the path routing arrangement 1 on channel N LOW ~ ' (N=0,1,.... ,9) and would always receive communication signals from the path routing arrangement on channel N HIGH (N=0,1,..... ,9).
Nescessarily, outgoing lines would then receive communications from the path routing arrangement on any of the LOW channels but would provide communications to the path routing arrangement on any of the ten HIGH channels in dependency on the incoming line with which it is linked. An advantageous consequence of this method of assignment is that it is no longer necessary to connect the BUSY LINES of every tenth horizontal transmission gate on the same front horizontal transmission track as was done with the previous method of channel assignment. If the BUSY LINES of every tenth vertical transmission gate are connected ( for example, the BUSY LINES of vertical gates V1,1,99' GVl,ll,gg, GVl,2l,99~ --~ GVl 91 99)~ then it is assured that no other incoming line that would dictate occupation ~-of the same two channels will gain access to the same front horizontal transmission track once access is gained by one such line. For example, if a bi-directional link was established between incoming line Iolol and outgoing line ~9997 in FIGURE 1 communications signals from line Iolol to line ~9997 would be-on channel 1 LOW. Communications signals in the opposite direction would be on channel 1 HIGH. Incoming lines Iol11, Iol21, Iol31, ..., Iolgl (not shown) would be denied access to front horizontal transmission track Fl 99. Any other incoming line on vertical platform VPl would have access to track F
and would have further access to any cross horizontal track ; connecting to track Fl 99 through a horizontal gate. Such further access would depend only on whether the horizontal gate was disabled by a busy signal from another gate on the same cross horizontal transmission track - the BUSY LINES of hori-zontal transmission gates in this respect being connected in f the same manner as for the previous method of channel assignment.
If it now occurred,for example, that there was an attempted link between incoming line Iol25 (not shown~ and out-going line ~9997 when a link between incoming line Iolol and ~utgoing line ~9997 was already established, then the communi-cation from line ~9997 intended to be directed only to line I
would not be received on the channel (channel 5 HIGH) which the external equipment (not shown) connected to line Io125 would be conditioned to receive.
However, as was discussed with respect to the previous method of channel assignment,it is still preferable that the external equipment (not shown) associated with each outgoing line such as line ~9997 include means to detect the instance of access by a second incoming line such as line Iol25 ~not shown) and to send back a signal to which the external equipment (not shown) of line Iol25 is responsive. The reason is to condition the external equipment associated with line Iol25 and prevent the generation by such equipment of the control signal sequence 5800 HZ - 5400 ~Z - 6000 HZ - t9-7-DIscoNNEcT) on a 2 MHZ carrier thereby causing horizontal transmission gate GHl 99 97 to close and break the link between line Iolol and line ~9997. Pre-ferably such conditioning signal would not prevent the generationof the control signal sequence 5800 HZ - 5800 HZ - 440C HZ -5000 HZ - 6000 HZ (9-9-2-5-DISCONNECT) required to close vertical transmission gate GVl 25 99~
The use of path routing arrangement 1 in a communication system will be now described with reference to FIGURE 8 which is a symbolic diagram illustrating certain basic aspects of a ~;
i communications system that interconnects a plurality of audio/~ideo - subscriber terminals T (To,Tl, ~ Tgggg) through an exchange 1 ;~
. ,, ~ .
;~. to enable bi-directional audio/video communications links to be established between calling ones and called ones of the ; subscriber terminals. Only two subscriber terminals Tj (PARTY A) , and Tk (PARTY B), and portions of the system associated immediately therewith are shown.
For purposes of illustration it will be assumed in particular instances that PARTY A is identified by the number "4828" and that PARTY B is identified by the number "8764".
With each subscriber terminal T (To,Tll ...,Tg999) there is associated line equipment E (Eo,El, ~Egggg) located within the exchange 1. Only line equipment Ej and Ek is shown.
'0 Terminal lines L (Lo,Ll ....,Lg999) which may, for example, be coaxial cable provide a bi-directional transmission path between the subscriber terminals T and their respective line equipment E - only lines Lj and Lk being shown.
In general, it is contemplated that subscriber terminals T may be remote from exchange 1 and accordingly a portion of each terminal line L is common with nine other such portions. Thus, in FIGURE 8, portion Ljp of 8 line Lj (i.e. the portion of line Lj between points 22 and 23 of line Lj) may be thought of as common with terminal line portions Ttj+l)p, ...., T(j+g)p.
Similarly, portion Lkp of line Lk may be thought of as common with prtin L(k+l)p' ~L(k+g)p; it being understood that the j-series of lines does not overlap with the k-series of lines.
Ten subscriber terminals T share the line portions because it is assumed, as with communications signals through the path routing arrangement, that up to 20 communication channels may occupy a ` terminal line. In particular, it will be assumed that each sub-' scriber terminal, depending on the last digit of its terminal number, transmits on a LOW channel in accordance with TABLE A
and receives on a corresponding HIGH channel in accordance with - 20 TABLE A. (For this purpose reference to "from an incoming line"
or "from an outgoing line" as appears in Table A should be ignored).
Thus, for example, PARTY A in FIGURE 8 (number 4828) transmits on channel 8 LOW (142 MHZ) and receives on channel 8 HIGH (Z42 MHZ).
Likewise, PARTY B (number 8764) transmits on channel 4 LOW (118 MHZ) and receives on channel 8 HIGH (218 MHZ).
The line equipment E of each subscriber terminal T is connected by two bi directional transmission paths (for example, coaxial lines) to the path routing arrangment 1 of FIGURE 8. As shown by the example of line equipment Ej and Ek, one such - 30 path is an incoming line Ij or Ik, as the case may be; the other 1~84183 such path is an outgoing line ~j or ~, as the case may be. The connectiOn of incoming and outgoing lines to the path routing arrangement was discussed with reference to FIGURES 2(a) and 2 (b). Also, the identification of incoming and outgoing lines ;
was discussed, but as can be seen in FIGURE 8 theidentification of a given incoming or outgoing line has been arranged to correspond with the identification of the subscriber terminal T with which it is associated.
The line equipment E of any subscriber terminal T has three basic modes of operation: (1) a calling mode of operation where the subscriber terminal with which it is associated is the terminal from which a call is placed; (2) a called mode of operation where the subscriber terminal with which it is associated ,1 ~
is the terminal to which a call is placed; and (3) a standby mode of operation in which the sbuscriber terminal is neither in the called or calling mode of operation. In the calling mode of ' operation the line equipment Ej, for example, provides circuit paths between the terminal line Lj and the incoming line Ij for for communications from the calling subscriber terminal to the called subscriber terminal, and for communications from the called subscriber terminal to the calling subscriber terminal.
In the called mode of operation similar circuit paths are pro-vided between the terminal line Lj and theoutgoing line ~
The line equipment E also provides control signals to control the operation ofthe transmission gates in path routing arrangement 1 of FIGURE 8. In the description that follows it is assumed that such control signals are provided over the incoming lines associated with calling subscriber terminals rather than over separate circuit lines from the line equipment to the gates. Generally, using by way of example the particular sub-~L~84183 scriber terminals shown in FIGURE 8, the line equipment operates as follows: On a call from PARTY A to PARTY B, the line equipment Ej of PARTY A, starting from its standby mode of operation is first "seized" by an appropriate command from sub-scriber terminal Tj which seizure switches line equipment Ej to the calling mode of operation. The line equipment Ej is then conditioned to receive further commands from the subscriber terminal ,, ~
Tj and in response thereto to provide selected code signals over ~ incoming line Ij to open the desired gates in the path routing -!- arrangement. On a call from PARTY A to PARTY B, and assuming access can be gained to all necessary transmission tracks (i.e.
no BUSY SIGNALS), such control signals are coded to open vertical transmission gate GV48 28 87 and horizontal transmission gate GH48 87 64 thereby defining a transmission path including these gates through path routing arrangement 1 between incoming line Ij and outgoing line ~k If the call had been from PARTY B to PARTY A, g Gv87~64~48 and GH87,47 28 would have been opened and the defined transmission path would have been between incoming line Ik and outgoing line Referring to path routing arrangement 1 as shown in FIGURE 8, it will be appreciated that with the exception of vertical transmission tracks V48,28 and V87,64, appearing within the arrangement roughly approximates the geometric locations of the two possible paths between PARTY A and PARTY B
in the three dimensional structure of FIGURE 1. The x-z axes in FIGURE 8 correspond to the x-z axes shown in FIGURE 1. For example, in FIGURE 8 front horizontal transmission track F48 87 is approximately where it should be (although its width is greatly exaggerated) considering that it is on the 49th vertical platform (not shown) of 100 vertical platforms (not shown) 1~8418-3 stacked in vertical stack 8 between side walls 7b and 7a - the first such platform being adjacent side wall 7b.
Of course, the particular design of line equipment ; will depend upon a number of factors including: the character of control signals the line equipment receives from the sub-scriber terminal; the character of control signals the line equip-ment must provide to operate the transmission gates of the path routing arrangement and the means whereby such control signals are transmitted to the transmission gates (i.e. as an input to the path routing arran~ement from incoming lines, or, as an input to the path routing arrangement on control signal lines . . - .
separate from the licensing lines); the conditioning action that the line equipment is required to perform on communications sig-nals to maintain proper frequency division of channels; and, the character of control signals the line equipment receives from or ~3 sends to other line equipment.
With regard to the maintenance of proper frequency division, it will be appreciated that,depending on channel ~-assignmentsthrough the path routing arrangement, and depending on the receiving and transmitting channels of the ~subscriber terminal, the line equipment of a particular subscriber terminal may be required to translate the carrier frequency of communica-tions signals it receives from the subscriber terminal, or from its associated incoming or outgoing line. FIGURE 8 (a) shows a number of possible channel assignments that maintain a division of frequency along various portions of the transmission path between PARTY A and PARTY B when PARTY A is the calling party. Path routing arrangement 1 is shown superficially in FIGURE 8 (a) because it is assumed that the communications link therethrough is established.
1o84l83 ` In FIGURE 8 (a), carrier frequencies along various portions in a glven direction of transmission (as indicated by ~ .
the arrows) are indicated generally by fA~ fA~ fB and fB for . each of four methods of channel assignment. The particular ~ :
channels that would be occupied along each portion of PARTY A
. and PARTY B were identified by the numbers "4828" and "8764", ; respectively, is indicated in brackets beneath the generally ~` indicated carrier frequencies. As can be seen, irrespective of ~:~ the method of channel assignment, PARTY A always transmits on the carrier frequency fA (8LOW) and receives on the carrier frequency fA (8 HIGH), and, PARTY B always transmits on the carrier frequency fB (4 LOW) and receives on the carrier frequency fB (4 HIGH). Also, it can be seen that irrespective of the method of channel assignment, a division of frequency is maintained ~.
over the path through the path routing arrangement 1 included in portion 2.
j The first and fourth methods of channel assignment shown in FIGURE 8 (a) have been previously discussed in the limited context of path routing arrangement 1 per se.
' 20 As indicated by the first method, the channel which is occupied for transmission from incoming line Ij (I4828) to g g ~k (~8764) is determined by the last digit identifying the incoming line Ij and is a LOW channel (8 LOW~; and the channel which is occupied for transmission from outgoing line ~k to incoming line Ij is determined by the last digit identifying the outgoing line ~k and is a HIGH channel (4 HIGH). According to the first method, it can be seen that line equipment Ej in the calling mode of operation is not required.to translate the carrier frequency fA of signals it receives from line Lj because the carrier frequency at its output to line Ij is the same.
1084~83 ., However, line equipment Ej may be required to translate the carrier frequency fB of signals received from line Ij because the carrier frequency fA at its output to line Lj is not ~ necessarily the same. For the example shown, frequency translation is clearly required to convert channel 4 HIGH to channel 8 HIGH, but would not be required if the number of PARTY B had been, for example, "8768". Also, according to the first method of channel assignment, it can be seen that the line equipment j Ek in the called mode of operation is required to translate carrier frequency in both directions of transmission - to convert ; a LOW channel to a HIGH channel for signals received fr~m line ~k and to convert a LOW channel to a HIGH channel for signals received from line Lk.
In the fourth method of channel assignment shown in FIGURE 8 (a) it can be seen that the channels occupied in path routing arrangement 1 are completely determined by the last digit identifying the incoming line. Consequently, as can be seen, line equipment Ej in the calling mode of operation is not required to translate carrier frequencies in either direction of transmission, but, line equipment Ek in the called mode of operation is required to translate carrier frequencies -;-in both directions of transmission.
The second and third methods of channel assignment shown in FIGURE 8 (a) service to indicate that other methods of channel assignment are possible. However, these additional methods certainly do not exhaust the possibilities.
Moreover, it might be noted that it is not necessary that the fre-quency bands occupied by the twenty possible channels that may, in general be carried over a terminal line L (portions 1 and 3 in FIGURE 8 (a)) do not necessarily have to be the 1~34183 same frequency bands occupied by the 20 possible channels in a defined path through path routing arrangement 1 (portion 2 in FIGURE 8 (a) - although there would of course be a correspondence between frequency bands. For example, in method 1 shown in FIGURE 8 (a), the carrier frequencies in portion 2 could theoretically be for example 1.5 fA and 1.5 fB ' or for example, fA + 50 MHZ and fB + 75 MHZ, rather than fA and fB, respectively, as indicated.
For some methods of channel assignment, the system must include means whereby the line equipment of a calling subscriber terminal can condition the line equipment of a called subscriber terminal to transmit to the calling subscriber terminal on a desired carrier frequency. For example, referring to method 4 in FIGURE 8(a), it can be seen that line equipment E~
receiving channel 4 LOW on line Lk is required to transmit on ; channel 8 HIGH to line k In general, line equipment Ek in the called mode of operation for method 4 may be required to transmit on any of 10 HIGH channels but cannot "know" which HIGH channel absent some identification from the calling party.
Where a requirement for such identification arises, it is contemplated that the line equipment of a calling party, in addition to providing control signals to define a path through the path routing arrangement, will also provide a control signal to the line equipment of the called party which latter control signal identifies the calling party. Such identifying control signal may, for example, be an audio tone in accordance with Table B superimposed on, for example, a 3 MHZ carrier signal -such audio tone being a "home tone" representing the channel number (the distinction between HIGH and LOW channels not being a matter for concern) of the calling party. The line equipment i. ` 1~4183 ,. .
of the called party, receiving the "home tone" on a 3 MHZ carrier - would include channel selection means responsive to the home ~- tone to select the carrier frequency on which the line equipment of the called party transmits to its outgoing line. Thus, for example line equipment Ej would transmit a 5600 HZ (Channel 8) home tone on a 3 MHZ carrier to line equipment Ek over the defined path from Ej to Ek causing line equipment Ek to transmit to line .
~k on channel 8 HIGH.
The same principles of "home tone" control may be used to tune a receiver in the line equipment ofa called party to ~.
receive a desired channel. For example, referring to method 1 or method 4 in FIGURE 8(a), a 5600 HZ (Channel 8) home tone on a 3 MHZ carrier could be used to tune a receiver in line equipment Ek to receive channel 8 LOW.
Once having decided on the desiredperformance of a system such as is shown in FIGURE 8 and having regard to the characteristics of the transmission gates and the character of control and communication signals from the subscriber terminals, then the design of line equipment to achieve the desired system response will be a routine matter to those skilled in the art.
As an illustration of one embodiment for line equipment, a communications system wherein channel assignments are in accor-dance with the first method of channel assignment shown in FIGURE
8(a) will now be considered with reference to FIGURES 9 to 11. A
number of assumptions will be made, and they are as follows:
(a) The transmission gates used in the path routing arrangement are of the type shown in FIGURE 7. All the ~:
BUSY LINES 109 (not shown in FIGURE 7 but see discussion relating FIGURE 7 to FIGURE 5) of vertical transmission gates on a given front horizontal transmission track are connected to each other and all BUSY LINES 109 of horizontal transmission gates on a given cross horizontal transmission track are connected to each other.
(b) Carrier frequencies transmitted from a subscriber terminal correspond, as previously discussed, to the last digit identifying the subscriber terminal. The first six megahertz of baseband is assigned to carrier video and the 7.5 MHZ baseband frequency for each channel is used as a subcarrier for audio.
(c) Audio intelligence tie. voice frequency) appears below 4 KHZ audio control signals appear out of band at or above 4 KHZ in accordance with TABLE B. Audio digit tones -~
(0 to 9) are produced by a subscriber terminal in response, for example, to the manual depression of a desired digit button on the subscriber terminal. In addition, a 6000 HZ DISCONNECT tone is produced by a subscriber terminal in response, for example, to hanging up a receiver of the subscriber terminal. Further, a 6200 HZ SEIZURE tone is produced by a subscriber terminal in response, for example, to picking up the receiver of the audio terminal.
(d) The line equipment is line equipment Ej for PARTY A
(No. 4828) in FIGURE 8. The lines Lj, Ij and Oj shown in FIGURE 9 thus correspond to the lines Lj, I j and Oj shown in FIGURE 8.
Accordingly, signals arrive on line Lj on a 170 MHZ
carrier (channel 8 LOW), and signals leaving on line Lj leave on a 270 MHZ carrier (channel 8 HIGH). In the calling mode of operation, communications signals leaving on line Ij leave on a 170 MHZ carrier (channel 8 LOW) and communications signals arriving on line Ij arrive on a carrier within the band from - 1~)84183 : ,:
; 200 MHZ to 300 MHZ (one of the channels 0 to 9 HIGH). In the called mode of operation communicationS signals arriving on line Oj arrive on a carrier within the band from 100 MHZ to 200 MHZ
(one of channels 0 to 9 LOW) and communications signals leaving ~ -on line Oj leave on a 270 MHZ carrier (channel 8 HIGH).
The operation of line equipment Ej in FIGURE 9 will first be considered assuming it is initially in the standby mode of operation, then switches to the calling mode of operation on a call to PARTY B (No. 8764) and then switches back to the standby mode of operation. The operation will then be considered assuming the line equipment is initially in the standby mode of operation, then switches to the called mode of operation, and then switches back to the standby mode of operation. In both cases reference will be made from time to time to FIGURES 10 and 11 which show elements of FIGURE 9 in greater detail.
(1) Standby-Calling-Standby Before line equipment Ej can provide control signals to line Ij to open the necessary gates in the path routing arrangement (not shown in FIGURE 9) to define a path to PARTY B and su~-sequently allow PARTY A to communicate with PARTY B, normallyopen switch SW must first be closed. In the standby mode of operation, this switch is open, but closes in response to a logical 1 input on line 522 from output c' of calling control circuit. As Will be seen, both control signals and communications signals provided to line Ij from line equipment Ej must pass through switch SWa.
Line equipment Ej will cause closure of switch SW if it is in the standby mode of operation and receives at its input from line Lj a 6200 HZ seizure tone on a 7.5 MHZ subcarrier in channel 8 LOW. All signals appearing on line Lj as an input 1~84183 , .
s to hybrid Hl appear at the output of hybrid Hl on line 500 to the input of channel filter 501. Channel filter 501 is a bandpass filter which passes only channel 8 LOW and blocks the other 9 LOW channels that may appear on line Lj as a result of the sharing of a portion of line Lj with other subscriber terminals. Likewise, channel filter 501 blocks all 9 HIGH
channels which appear on line Lj (ie. excluding 8 HIGH).
Assuming hybrid Hl is ideally balanced, channel 8 HIGH would not appear on line 500, but, if there is some unbalance, channel filter 501 blocks the signal.
Signals appearing within channel 8 LOW at the input of channel filter 501 appear at the output thereof on line 502 to the input of hybrid H2 which provides the input signal as an output to lines 503 and 504, still within channel 8. The output signal from hybrid H2 on line 503 is also the input to line receiver 505 which receives channel 8 and produces as an output on line 506 the baseband signal (0-6 MHZ video and 7.5 MHZ audio subcarrier). The baseband signal is passed through hybrid H3 which provides the baseband input on line 506 as an output on lines 507 and 508. The output on line 508 will not be considered for the moment because, as will be seen, it is only used when line equipment Ej is in the called mode of operation.
The ouput on line 507 is the input to input "a" of calling control circuit 509.
Calling control circuit 509 is a multi-function element shown in greater detail in FIGURE 10. In addition to controlling the operation of switch SWa, it also ensures that digit tones are provided to the path routing arrangement on the proper carrier frequencies (1 MHZ or 2 MHZ as the case may be). Additional functions that are preformed will be described as the description proceeds.
i~84183 Referring now to FIGURE 10, when a baseband signal appears on line 507, it is first filtered by high pass filter l9S
which removes the video component (0-6 MHZ) of the baseband signal, allowing only the audio subcarrier (7.5 MHZ) to pass to line 196.
Receiver 197 is a 7.5 M~Z receiver which receives the audio subcarrier on line 196 and produces at its output on line 198 audio intelligence (voice frequencyl plus audio control (out-of-band --4KHZ and above). High pass filter l9g removes the voice frequency range of the audio signal and passes only the out-of-band range to its output on line 200.
The remainder of calling control circuit 509 processesthe various audio control signals that may appear on line 200.
; The element which determines whether or not line equipment Ej is in the calling mode of operation is flip-flop FFS. Normally, its output on line 522 is logical 0. Consequently switch SW : -is FIGURE 9 will be open meaning that line equipment Ej is either in the standby mode of operation or the called mode of operation. The output of flip-flop FFS on line 522 will be switched to logical 1 if a 6200 HZ SEIZURE tone appears on line 200 provided line equipment Ej is not in the called mode of operation.
When a SEIZURE tone appears on line 200 it also appears on line 200a to the input of receiver detector R/DS which is tuned to receive and detect 6200 HZ. A 6200 HZ tone input causes the output of receiver detector R/DS on line 205 to switch to logical 1 which output is also one input of dual input logical AND gate ANDS. If the other input to gate ANDS from line 526 is also logical 1, the output of gate ANDS on line 206 to logical inverter INVS will follow the output of receiver detector R/DS
.30 on line 205. Then, the output of inverter INvs ~n line 207 to :
1~84183 the set input of flip-flop FFS will switch to logical 0 when the output of receiver detector R/DS, in response to a SEIZURE tone, switches to logical 1. At the termination of the SEIZURE tone, ; the output of inverter INVS switches from logical 0 to logical 1 thus providing a set command to flip-flop FFS causing output PS
to line 522 to switch to logical 1 from logical 0. Switch SWa in FIGURE 9 will then close and line equipment Ej is in the calling mode of operation.
As can be seen by referring to FIGURE 9, line 526 which is one input of gate ANDS in FIGURE 10, receives signals from output 'c' of called control ciruit 538. When line equipment Ej is in the called mode of operation, the signal at ouput c' of called control circuit 538 is logical 0 (the means will be discussed in more detail hereinafter with reference to FIGURE 11) which disables gate AND5 to prevent a seizure tone from providing a set command to flip-flop FFS. Nevertheless, a SEIZURE tone will be detected by receiver detector R/DS even if line equipment Ej is in the called mode of operation. As can be seen in FIGURE 10, the output of receiver detector R/DS on line 205 also appears as an output to line 525. Line 525, as can be seen from FIGURE 9, provides an input to input b of called control circuit 538. The response of called control circuit 538 to logical signals appearing on line 525 is of concern in the called mode of operation only and will be considered later.
Referring again to FIGURE 10, it can be seen that calling control circuit 509 includes four digit tone stages DTSl, DTS2, DTS3 and DTS4, only the first digit tone stage DTSl being shown in detail. The structure of each stage is identical the first, -each having three inputs al, a2 and a3, and four outputs a4, a5, a6 and a7. As can be seen, the output a4 is only used for 1~84183 ::
the first staye DTSl and the outputs a6, a7 are not used for the fourth stage DTS4. Each stage includes a receiver detector R/DT
which is widely tuned to switch to logical 1 if the signal appearing .
at its input (on line 225 for stage DTSl) is any of the 10 digit :
tones from 4000 HZ to 5800 HZ. Referring to stage DTSl by way of example, when the output of receiver detector R/DT on line 226 to the input of logical inverter INVT switches to logical 1, then the output of inverter INVT on line 227 to set input ST of ~.
flip-flop FFT switches to logical 0. The output of INVT switches back to logical 1 at the terminatlon of a tone detected by receiver detector R/DT thus providing a set command to flip-flop : -S ' -~
In the standby mode of operation, the output PT
of each flip-flop FFT is of all stages logical 0. These outputs sequentially switch from logical 0 to logical 1 at the termination of each successive digit tone. Such sequential control is determined by the sequential switching of normally open switch SWT of each digit tone stage 1 which switch closes in response to a logical 1 control input (on line 222 for stage DTSl) from dual input logical AND gate ANDT f each stage.
- Referring to stage DTSl it can be seen that one input of gate :
ANDT appears on line 220 from input a3 of stage DTSl; the other .
input appears on line 221 from complementary output PT of flip-flop FFT via line 229 from output PT. Complementary output PT
is the inverse of output PT: if PT=0, then PT-l; if PT=l, then PT=0. Thus, gate ~NDT is closed when the input to input a3 is logical 1 and the output PT of flip-flop FFT is logical 1.
Since the output PT of each flip-flop FFT is logical 0 in the standby mode of operation, the output PT of each flip-flop FFT will be logical 1. With the exception of stage DTSl, the input a3 of each stage will be at logical 0 in the standby mode of operation because this input is the output a6 of the previous stage (via lines 235, 237, 239 as the case may be) which output is taken from output PT of flip-flop FFT in each stage (ie.
via line 228 in stage DTSl). The input a3 of stage DTSl is connected to the output PS of flip-flop FFS by line 222 and the line to line 522 and is thus logical 0 when line equipment Ej is in the standby mode of operation.
As has been ~escribed, when line equipment Ej switches to the calling mode of operation at the end of a SEIZURE tone, ; the output PS of flip-flop FFS is logical 1. Then, the input a3 of stage DTSl becomes logical 1. Since output PT of flip-flop ; FPT in stage Dl'Sl is also logical 1, gate ANDT produces a logical 1 output on line 222 causing switch SWT in stage 1 to close. The first digit tone that appears on line 200 and, through low pass filter 201, on line 203, (which tone would be ` 5600 HZ - the digit 8 - on a call from PARTY A to PARTY B) also appears as an input on line 200c to input al of stage DTSl and is passed over line 224 and through switch SWT which switch is now closed to line 225. So long as the tone appears ~n line 225 it also appears via line 231 at output a5 of stage DTSl.
When the first digit tone terminates, the output PT
of flip-flop FFT in stage DTSl switches to logical 1 and output T f flip-flop FFT in stage DTSl switches to logical 0. The logical 0 condition of output PT causes switch SWT in stage DTS
to open. The logical l-condition of output PT off flip-flop FFT in stage DTSl which condition appears at input a3 of stage DTS2 causes switch SWT in stage DTS2 to close because the output PT of flip-flop FFT in stage DTS2 is also logical 1. Stage DTS2 responds to the second digit tone that appears on line 203 (which tone would be 5400 ~Z - the digit 7 - on a call from PARTY
A to PARTY B) in the same manner that stage DTSl responded to the first tone. During the continuance of the second tone at input al of stage DTS2, the same tone would appear at output a5 of stage DTS2. In the same manner, the next two digit tones (5200 HZ-4800 HZ the digits 6-4) would appear sequentially at outputs a5 of stages DTS3 and DTS4 respectively.
When a tone appears at an output a5 of one of the ' digit tones stages of FIGURE 10 it is directed through either amplifier AMPa to line 511 or amplifier AMPb to line 512 which lines are, respectively, inputs to the 1 MHZ and 2 MHZ modulators shown in FIGURE 9. As can be seen in FIGURE 10, each amplifier has three inputs, one input of which derives in each case from the output of disconnect filter 202. The other two inputs to amplifier AMPa are from output a5 of stage DTSl on line 233 and output a5 of stage DTS2 on line 240. The other two inputs to amplifier AMPb are from output a5 of stage DTS3 on line 241 and output a5 of stage DTS4 on line 242.
Both amplifiers AMPa and AM2b operate as summing amplifiers producing at their outputs the tone that appears at one of their three inputs. The input impedance of each input to the amplifiers should be sufficiently high to avoid having a signal on one input line appear on another input line of the same amplifier with sufficient power to be detected by the receiver detector associated with the other input line. Otherwise, for example, the output PT of flip-flop FFT of stage DTS2 could be switched to logical 1 at the termination of the first tone.
Then, switches SWT in stages DTS2 and DTS3 would he closed when the second digit tone appeared and the sequential operation would be destroyed. Alternatively, any tendency for this result to i~S4~83 occur will be suppressed by the insertion of buffer amplifiers on each of lines 215, 233, 240, 241 and 242.
Assuming then that such irregular operation does not occur, the first two digit tones that appear in sequence on line 203 will also appear in sequence at the output of amplifier AMPa to line 511, or, as shown in FIGURE 9, at output a'of calling control circuit 509. Likewise, the next two digit tones that appear in sequence on line 203 will also appear in sequence at the output of amplifier AMPb to line 512, or, as shown in FIGURE 9, at output b' of calling control circuit 509.
Referring now to FIGURE 9, the tones appearing on line 511 are the modulating input to modulator MODl, the output of which modulator is a 1 MHZ carrier on line 513 to hybrid H7 - the carrier being modulated by the modulating input. Hybrid H7 produces at its output on line 515 the signals that appear on lines 513 and 514. The signal that appears on line 514 is a 2 MHZ carrier from modulator MOD2 which carrier is modulated by tones appearing at the input to modulator MOD2 on line 512.
The 1 MHZ and 2 MHZ modulated carrier signals are combined by hybrid H8 with the channel 8 LOW signal appearing on line 504. Thus, the combined channel 8 LOW signal and mod-ulated 1 MHZ and 2 MHZ carrier signals appear at the output of hybrid H8. Switch SWa which is now closed passes the combined signals to the input of line amplifier AMPl. From the output of amplifier AMPl the combined signals appear on line 518 to the input of hybrid Hg which hybrid provides the output of line equipment Ej to line Ij.
The sequence of tones appearing on the 1 MHZ and 2 MHZ
carriers will first cause vertical transmission gate GV48 28 87 (see FIGURE 8) to open and then cause horizontal transmission 1~84183 gate GH48 87 64 (see FIGURE 8) to open - assuming that the gatcs are generally as shown in FIGURE 7 and assuming th.at the gates are not disabled by busy signals. If the gates were disabled, then of course a path to PARTY B would not be established.
FIGURE 9 does not show means that would aetect that a path has not been established - ie. there is no provision for a busy signal.
FIGURE 9 does show a meanstoprovide a dial tone indicating that line equipment Ej has switched to the calling mode of operation. When the output e' of calling control circuit 509 is logical 1, normally open switch SWc is caused to close allowing a dial tone appearing on a 7.5 MHZ audio subcarrier line 528 at the output of dial tone generator 527 to pass through switch SWc to the input of hybrid H5 on line 529. The dial tone per se may ~e any audible frequency or frequencies attractive to the human ear. The 7.5 MHZ modulated subcarrier signal appears at the output of hybrid H5 on line 533 to the input of hybrid H4, and then at the output of hybrid H4 on line 545 to the input of line transmitter 546. Inputs to line transmitter 546 are transmitted at its output to line 547 on the 270 MHZ
channel 8 ~IGH carrier frequency required for reception by the subscriber terminal of PARTY A. The line transmitter output on line 547 is amplified by line ~lP3 and appears as the input to hybrid Hl on line 548 which hybrid provides the output on line Lj to subscriber terminal Tj (not shown in FIGURE 9.) Referring to FIGURE 10, it can be seen that a logical 1 condition on line 524 to switch SWc in FIGURE 9 will only appear so long as the output of dual input logical AND gate 210 is logical 1. The output of gate 210 is logical 1 only if the input thereto on line 210 from the output PS of flip-flop FFS tvia 1~84~
the line "to line 522") is logical 1 and if the input thereto on line 232 from output a4 of stage DTSl is logical 1. It may readily be concluded that a dial tone will last from the time line equipment Ej switches to the calling mode of operation and until the termination of the first digit tone.
Assuming ~hat a bi-directional communications link is established between PARTY A and PARTY B, communications signals from PARTY B appearing at the input of hybrid Hg from line Ij will appear at the output of hybrid Hg on line 530 to front wall receiver 531. Since in general such communications signals may occupy any one of ten HIGH channels, and since line equipment E
shown in FIGURE 9 does not include means to ;automatically tune front wall receiver 531 for the channel it will receive, then, the receiver 531 must be widely tuned to receive any of the 10 HIGH channels.
The output of front wall receiver 531 on line 532 to hybrid H5 is the baseband (0-6 MHZ video and 7.5 MHZ audio subcarrier) of the channel being received. From the output of hybrid H5 on line 533, the baseband signal follows the same path and undergoes the same conditioning as was described for the 7.5 MHZ dial tone subcarrier. The baseband signal is transmitted to subscriber terminal Tj (not shown in FIGURE 9) on channel 8 HIGH.
It is thusapparent that, in the calling mode of operationand except when the input from line Ij is channel 8 HIGH, communication signals passing through line equipment Ej from line Ij to line Lj undergo carrier frequency translation as a result of the combined effect of front wall receiver 531 and line transmitter 546.
; 30 Line equipment Ej shown in FIGURE 9 switches from the calling mode of operation back to the standby mode of operation 8 ~
in response to a 6200 DISCONNECT tone appearing on the proper subcarrier and carrier frequencies as an input on line Lj. When such tone appears it detected by calling control circuit 509 in much the same manner as other audio control signals. Referring to FIGURE 10, a tone appearing at the input of disconnect filter 202 on line 200b will appear at the output of filter 202 if it is a 6000 HZ DISCONNECT tone. This filter is a band pass filter sharply tuned to block control tones other than 6000 HZ.
Receiver detector R/Dd receives the output of filter 202 on `
line 212 and switches to logical 1 at its output on line 213 if a DISCONNECT tone appears at its input. (Because of the filtering action of filter 202 it is not necessary that receiver detector R/Dd be sharply tuned for 6000 HZ). Through logical inverter INVd and line 214 to reset input RS of flip-flop FFS, flip-flop FFS is reset to its standby mode condition at the termination , ~
of a disconnect tone. Likewise, flip-flops FFT in stages $
DTSl to DTS4 receive, via lines 216, 234, 236 and 238, reset commands at their inputs RT at the same time.
As can be seen, any DISCONNECT tone that appears at the output of disconnect filter 202 on line 212 becomes ~n input~
(via lines 215 and 219) to both amplifiers AMPa and AMPb -in the result modulating both the 1 MHZ and 2 MHZ carrier signals being transmitted to the line equipment on line Ij. At the termination of the DISCONNECT tone on the 1 MHZ and 2 MHZ carriers, the open transmission gates in the path routing arrangement on the path between PARTY A and PARTY B are caused to close.
The purpose of low pass filter 201 can now be seen.
In passing only audio control signals below 6000 HZ, filter 201 does not allow a DISCONNECT tone to operate the receiver detectors R/DT associated with flips-flops FFT in the stages DTSl to DTS4.
~ ':
1~8418~ -Otherwise, unless such receiver detectors were designed not to respond to the 6000 HZ DISCONNECT tone, a flip-flop FFT might receive a set command and a reset command at the same time.
This situation would arise where a DISCONNECT tone was received before a digit tone sequence was complete. One of the switches SWT would be closed meaning that its corresponding receiver detector R/DT would detect the DISCONNECT tone at the same time as receiver detector R/Dd. An alternative way to control this situation would be to insert a time delay in line 216 - for example, two logical inverters connected in series.
(2) Standby-Ca_led-Standby Ordinarily, line equipment Ej switches from the standby mode of operation to the called mode of operation on detection of a 2 MHZ carrier signal input from line ~j to Hlo. The one exception is where the condition on line 523 from line 522 to input c of called control circuit 538 is logical 1 meaning that PARTY A must have called his own number.
The 2 MHZ carrier is detected by called control circuit 538 receiving its input at input a from hybrid Hlo - 20 via lines 534 and 535. As can be seen in FIGURE 11, the input to called control circuit 538 from line 535 is received by receiver detector R/DC which receiver is tuned to 2 MHZ and produces a logical 1 output on line 600 whenever a 2 MHZ signal is detected. Line 600 is one input of dual input AND gate ANDC, the output of which gate on line 602 switches to logical 1 if the input on line 601 from logical inverter INVC is logical 1 ` when a 2 M~Z signal is detected. The output of inverter INV
will be logical provided its input on line 523 is logical 0 (ie.
if A has not called his own number). When the condition on line 602 switches to logical 1, three events occur. Firstly, flip-,,~
~ -69-1~84183 flop FFC is set by the logical 0 to logical 1 transition occuring at its inpu-t Sc. Accordingly, the output to line 540 from output Pc of flip-flop FFC switch to logical 1. The logical 1 condition on line 540 closes normally open switch SWd which :~ :
allows signals appearing at the output of ring tone generator 541 on line 542 to pass through switch SWd to the input of hybrid H6 on line 543. As in the case of dial tone generator 527, ring tone generator produces audibly attractive ring tones on a 7.5 -MHZ audio subcarrier for ultimate reception by subscriber terminal L0 Tj. The input to hybrid H6 on line 543 appears at the output of ;
- hybrid H6 on line 544 to the input of hybrid H4 from the output ~, of which, on line 545, the signal follows the same path and undergoes the same conditioning as inputs to hybrid H4 from line 533. The ring tone terminates when flip-flop FFC in FIGURE 11 ~.
receives a reset command at input Rc from line 605 through logical OR gate ORC from line 525. As can be seen from FIGURE 10 I a reset command will be provided to line 525 when receiver detector R/DS detects a SEIZURE tone (ie. when the receiver at subscriber terminal Tj is picked up).
At the same time that output Pc of flip-flop FF
in FIGURE 11 switches to logical 1, the output of logical ; inverter INVc, receiving its input on line 603 from line 602, switches to logical 0. The logical 0 condition appears on line 526. As can be seen in FIGURE 10, a logical 0 condition on line 526 disables gate ANDS so that a SEIZURE tone cannot now cause - r a set command to appear at input Ss of flip-flop FFS.
. Finally, when the condition on line 602 is logical 1, the output to line 539 from line 603 is also logical 1. The logical 1 condition on line 539 (from output a' of called control circuit 538 to switch SWb in FIGURE 9) causes normally open switch SWb to close thereby completing a transmission path from the output of hybrid H3 on line 508 to line 0j. As will be recalled, the signal on line 508 will be the baseband components of channel 8 LOW. These components are received from line 508 by back wall transmitter 510 and transmitted to line 519 on the 270 MHZ carrier for channel 8 HIGH. rrhe signal on line 519 ;
passes through switch SWb, now closed, to the input of line amplifier AMP2 from line 520. The output of line amplifier AMP
on line 521 appears at the input of hybrid Hlo on line 521, which hybrid provides the output on line ~j to the calling party.
Signals received from line 0j appear on line 534 at the input of back wall receiver 536 as well as the input of -~
called control circuit 538. Since back wall receiver 536 may be required to receive any of 10 LOW channels and since the line equipment does not include channel selection means to automatically tune the receiver tc receive particular channels, it must be broadly tuned to receive any of the ten LOW channels.
The output of backwall receiver 536 on line 537 to hybrid H6 is the baseband component of the channel at the output of hybrid Hlo on line 534 from the output of hybrid H6 on line 544, the baseband signals will follow the same path and undergo the same conditioning as signals from ring tone generator 541.
In the called mode of operation, it is thus apparent that communicatlons signals passing through line equipment Ej, either from line Lj to line ~j, or from line ~j to line Lj, will-- -s undergo carrier frequency translation. Channel 8 LOW received on line Lj is converted to channel 8 HIGH by the combined effect of line receiver 505 and back wall transmitter 510. Any channel (which channel will be a LOW channel) received on line ~j will 1~84~83 ~e converted to channel 8 HIGH by the combined effect of back wall receiver 536 and line transmitter 546.
As can be concluded from FIGURE 11, the called mode of operation for line equipment Ej in FIGURE 9 will endure only so long as a 2 M~Z signal is detected by receiver detector R/DC.
The 2 MHZ signal is of course the 2 MHZ carrier from modulator -~
MOD2 of the calling party's line equipment and will terminate when the calling party causes a DISCONNECT tone to be produced.
The transmission gates in the path routing arranqement are then caused to open breaking the path for the 2 MHZ carrier from the calling party to the called party. The output from the circuit of FIGURE 11 to line 526 returns to logical 1; the output to line 539 returns to logical 0; and since flip-flop FFC was previously reset when PARTY picked up his receiver, the line equipment E
has now returned to the standby mode of operation.
It may occur on a call to PARTY A that PARTY A will not pick up his receiver to generate the SEIZURE tone necessary to reset flip-flop FFC in FIGURE 11. Accordingly, one-shot multivibrator /Sc is included in called control circuit 538 to produce a reset pulse whenever receiver detector R/DC
switch from logical 1 to logical 0. Thus, when a negative ~ r switching transition from logical 0 to logical 1 appears on line 600 one shot multivibrator /Sc produces a logical 1 pulse at its output on line 604 to gate ORC. The same pulse ~ appears at the output on line 604 to gate ORC. The same pulse -~ appears at the output of gate ORC on line 605 to reset input Rc of flip-flop FFC. The logical 0 to logical 1 switching transition on the leading edge of the pulse causes flip-flop FFC to be reset. Hence, if PARTY A does not pick up his receiver, calling control circuit 538 will nevertheless be . . ..
1~84~83 returned to its initial condition at the termination of a 2 ~HZ input detected by R/DC. Line equipment Ej will then be in the standby mode of operation.
(3) General There are some additional observations that might be made regarding line equipment Ej in FIGURE 9.
Firstly, it will now be apparent that certain elements of FIGURE 9 are only operative depending on the mode of operation.
For example, back wall transmitter 510 and back wall receiver 536 are only operative in the called mode of operation. Front wall receiver 531 is only operative in the calling mode of operation.
Line transmitter 546 is operative in the called mode of operation or the calling mode of operation. Line receiver 505, however, is operative in all three modes of operation - standby, calling, and called. Although not shown in FIGURE 9, it would of course be a simple matter to include means to switch such transmitters or receivers on or off, as required, depending on the mode of operation. A logical 1 signal is available as a control signal on line 522 in the calling mode of operation and a logical 1 signal is available on line 539 in the called mode of operation.
Secondly, as has been said, in the absence of means to automatically tune front wall receiver 531 and back wall receiver 536, such receivers must be widely tuned to receive any of 10 HIGH channels (in the case of receiver 531) or any of 10 LOW channels (in the case of receiver 536). Such wide tuning may cause undesirable noise in the system. Also, from earlier ~~
discussions, it will be recalled that it is contemplated that some embodiments of line equipment (then referred to as "external equipment") will be conditioned to receive particular channels to avoid interference when a front horizontal trans-mission track forms a part of the bi-directional link between ~84183 more than one pair of incomin~ and outgoing lines. (The latter situation does not arise where the line equipment is as shown in EIGURE 9 and the transmission gates are as shown in FIGURE 7 with ~he BUSY LINES of such gates connected in the manner aforesaid, but, whatever the reason for conditioning receivers to receive particular channels, the means in general may be the same).
With regard to FIGURE 9, it is evident that line equipment Ej will in all cases "know" in advance what channel will be received on line Ij from a called party. For example, when PARTY A calls PARTY B (No. 8764), it is known that the channel that will be received from incoming line Ij will be channel 4 HIGH. The "knowledge" as such may derive from output a5 of digit tone stage DTS4 of calling control circuit 509.
Such output is the digit tone corresponding to the last digit of the number of a called party. Where PARTY A calls PARTY B
the tone at output a5 would be 4800 HZ, representing the digit 4. I f FIGURE 12 illustrates how the tone appearing at ¦
output a5 of stage DTS4 may be used to condition line equipment Ej to receive a particular channel from incoming line Ij. Since ~20 the elements are very similar to elements previously described FIGURE 12 will only be considered briefly. As can be seen, a digit tone appear at output a5 will be the input to a ban~ of ten receiver detectors R/Dlo to R/Dlg in channel selection circuit 250, only four of which receiver detectors are shown in FIGURE 12.
Receiver detectors R/Dlo to R/Dlg are tuned to receive and detect the tones 4000 HZ to 5800 HZ (digits 0 to 9), respectively. When a digit tone is detected, the output of the receiver detector that detected the tone switches to logical 1. As can be seen, theoutput of each receiver detector is the set input of a corresponding ~30 flip-flop F~lo to F~lg, as the case may be. Likewise, the output of each receiver detector, through set/reset lines 0 to 9 is I
I' 1(~84183 the input of nine logical OR gates associated with the other nine receiver detectors. For example, the output of receiver detector R/D12 is the input of gates ORlo, ORll, OR13 or OR18 (not shown), and ORlg. Thus, when the output of a receiver detector R/Dlo to R/D19 switches to logical 1, the flip-flop FFlo to FFlg, as the case may be, associated with the receiver detector receives a set command causing its output Plo to Plg, as the case may be, to switch to logical 1 (or do nothing if such output is already logical 1). The logical 1 output of the receiver detector that switched also appears, through the OR gates associated with the nine other receiver detectors, at the reset inputs of the other flip-flops associated with the nine other receiver detectors. Accordingly, all such other flip-flops receive a reset command. The output of any such flip-flop that is not already logical 0 is caused to switch to logical 0.
The outputs P1o to Plg of fIip-flops FFlo to ~Flg control switches SW10 to SWlg, respectively, in front wall receiver 531, which, as now considered, is an all-wave 20 receiver, the tuning range of which is changed by switching tuned circuits of the receiver. Switches SW10 to SWlg are normally open but close in response to a logical 1 command ~ from the output Plo to Plg, as the case may be. Ordinarily, -~ only one such switch is closed depending on which output Plo to Plg is logical 1.
The design of all-wave receivers is well known as is the automatic switching of tuned circuits thereof to tune the receivers to receive a desired channel. Accordingly, the -~
detailed circuit design of such receivers will not be considered.
1~84183 Referring again to FIGURE 9, it is apparent that line equipment Ei cannot "know" the channel number of an input from line ~j unless it is told by the calling party. Thus back wall receiver 536 cannot be tuned in response to control signals initiated from line equipment Ej. Any automatic tuning means for receiver 536 must ultimately be controlled by the calling party.
FIGURE 13 (a) and 13 (b) illustrate how line equipment may be modified to allow a calling party to tune the back wall receiver 536 of a called party. As can be seen, FIGURE 13 (a) repeats some of the elementsof FIGURE 9 and includes in addition a 3 MH~ modulator MOD3 and a further hybrid H7a which receives inputs from the output of hybrid H7 on line 515 and from the output of modulator MOD3 on line 515a. The output of hybrid H7a is on line 515a to hybrid H8. Modulator MODl receives as a modulating input on line 515c a HOME TONE which identifies line equipment Ej and consequently the subscriber terminal Tj associated therewith. The HOME TONE, which may be produced by a simple oscillator (not shown) included in line equipment Ej, has a frequency corresponding to the last digit of the number identi-fying subscriber terminal Tj (No. 4828) - in the present case 5600 H~ representing the digit 8. Thus, when PARTY A is the calling party, the output to line Ij includes a 3 MH~ carrier modulated by a 5600 H~ HOME TONE.
For purposes of responding to a HOME TONE received on line ~j , line equipment Ej now includes a home tone receiver 535a as shown in FIGURE 13 (b) plus a modified version of FIGURE
12. Home tone receiver 535a is tuned to receive 3 MHZ modulated carrier inputs from line 535 and produce at its output "to input X" the modulating frequency or home tone. Input X is the 1~34183 ::
input "X" shown in FIGURE 12 wherein (a) front wall receiver 531 is now to be considered as back wall receiver 536; (b) the designation "FROM aS" (FIGURE 10) is to be ignored; (c) the designation~"530" is now to be taken as "534"; and (d) the designation "532" is now to be taken as "537". Also, tuned circuits 10 to 19 in FIGURE 12 are now tuned for LOW channels rather than HIGH channels as shown.
From the description of the tuning of front wall receiver 531, it will readily be concluded that back wall receiver 536 will be tuned for a particular low channel depending on the frequency of the HOME TONE from a calling party.
In some embodiments of line equipment, it may be ~, desirable to tune line transmitters to transmit on a particular channel. For example, according to the fourth method of channel assignment shown in FIGURE 8(a), it is apparent that the line equipment Ek of PARTY B (the called party) must convert channel 4 LOW inputs received on line Lk to channel 8 HIGH outputs to ;
' line ~k~ Since channel 8 HIGH is a channel determined by PARTY A, then line equipment Ek must be conditioned to transmit on such channel by control from PARTY A. Although line equipment Ej shown in FIGURE 9 was not designed for the fourth method of ~-channel assignment shown in FIGURE 8(a), it may readily be concluded that with some modification and the use of HOME TONES
to tune back wall transmitter 510 as well as back wall receiver 536, then, the desired channel assignment will be achieved. Front wall receiver 531 may now be permanently tuned to receive only channel 8 HIGH since this will always be the channel input on line Ij. However, in the called mode of operation the channel received by back wall receiver 536 (a LOW channel) and the channel transmitted by back wall transmitter 510 (a HIGH channell will vary depending on the last digit of the number identifying the calling party. Back wall receiver 536 may be tuned by a HOME
1~84~83 TONE in the manner aforesaid. Similarly, the same HOME TONE
may be used to discretely control the transmitting carrier frequency of back wall transmitter 510 by switching tuned circuits of the transmitter carrier frequency oscillator. -Similar to the case of receivers, the design of transmitters to automatically transmit on one of a number of transmitting frequencies is well known and detailed circuit design will not be considered.
The hybrids shown in FIGURES 9 and 13(a) may be conventional resistive hybrids as shown in FIGURE 14 comprising resistors Rx, Ry and balancing lmpedance Zb The loss through each will be approximately 6 dB, but such loss may be recovered by the line amplifiers AMPl, AMP2 and AMP3 which also compensate for losses in the transmission paths outside the line equipment Ej.
Line equipment_Ej as shown in FIGURE 9 is not suitable to control transmission gates such as are shown in FIGURES 5(a) and 5(b) which require that coded control signals be received within predetermined time intervals. For the circuit of FIGURE
9, the control signals which originate at first instance from the subscriber terminal Tj (not shown in FIGURE 9) in effect flow through line equipment Ej via calling control circuit 509 from line Lj to line Ij at a rate determined by the rate of activity at the subscriber terminal. To produce the control signals required to operate transmission gates such as are shown in FIGURE 5(a) or 5(b), it is contemplated that the calling control circuit would include a storage means to record the number of the called party, and then produce the necessary control signals to close or open the transmission gates during a rapid playback of digits of the recorded number - the order of the digits in the playback depending on whether the transmission - ~84183 gates were to be closed or opened. For the transmission gate of FIGURE 5(b) used as a vertical transmission gate, the two digit tones represen-ting the identification of the incoming line would be added to the playback sequence following the two digit tones identifying the connecting front horizontal trans-mission track. A playback sequence would be initiated on a call from one party to another when the last digit tone identifying the called party is detected by the calling party's called control circuit. Likewise, a playback sequence would !. be initiated when a DISCONNECT tone is detected by the calling party's called control circuit.
FIGURE 15 is a circuit diagram of a transmission gate ' which uses diodes, rather than a mechanically moving part, such as switch SWl in FIGURE 5, to perform gating operations between transmission tracks. The transmission gate in FIGURE
15 comprises two diodes Dgl and Dg2 which are connected back-to-back on their anode sides. Preferably, the diodes are high frequency PIN diodes. The cathode side of diode Dgl is connected to gate contact line 24 and the cathode side of diode Dg2 is connected to gate contact line 25. The transmission gate also comprises two resistors Rgl and Rg2 connected in series between bias control line 26 and the connection between the anodes of diodes Dgl and Dg2. A capacitor Cg provides a circuit path between such two resistors and the outer conductor of the transmission tracks.
The operation of the transmission gate shown in FIGURE 15 is as follows. When the voltage applied to bias control line 26 is zero with respect to the outer conductor of the transmission tracXs (which may be considered as ground), then diodes Dgl and Dg2 are subs-tantially non-conductive. The ` 11[~84183 transmission of R. F. communication signals between transmission tracks is inhibited and the gate is closed. When a positive voltage is applied to bias control line 26, then diodes D
and Dg2 are forward biased and will be conductive to allow the transmission of R. F. communication signals between transmission tracks - the gate is then open. During such transmission, capacitor Cg aids to suppress the appearance of R. F. signals on bias control line 26. It may be noted that the circuit path for bias voltages applied to bias control line 26 can be completed by load terminations (not shown in FIGURE 15~ on the transmission tracks.
In FIGURE 15, it is assumed that the transmission gate is not controlled by code input signals provided as an input to a transmission track, thus there is no probe shown such as probe 87 in FIGURE 5. It is thus assumed that the bias voltages applied to bias control line 26 are determined by means other than code input signals to a transmission track.
As depicted, the transmission gate shown in FIGURE 15 is not in any sense coded, however, it plainly could be coded if so desired. For example, bias control line 26 could be the output of a binary or a binary-coded-decimal comparator having a plurality of digital (logical 0 or logical 1) input lines. The output voltage of the comparator to bias control line 26 would be the voltage necessary to open the transmission gate if and only if preselec-ted ones o~ the digital input lines were at loyical 1 and the remainder of -the diyital inpu-t lines were at lo~ical 0. Theimplementation of such control will be obvious to those ski]led in the ar-t.
- ~0 -1~84183 The branched path, path routing arrangement (FIGURE 1) described in detail herein is characterized by a decimal based system of organization and is symmetric in structure - that is, there are 100 (10 x 10) vertical platforms, each having 100 (10 x 10) vertical tansmission tracks, and 100 (10 x 10) horizontal platforms, each having 100 (10 x 10) cross horizontal transmission tracks.
` For each possible pair of platforms consisting of a vertical plat-form and a horizontal platform, there are 100 (10 x 10) inter-connecting front horizontal transmission tracks. Also, the arrangement was described in terms of being used in a bi-directional communication system wherein 20 (10 x 2) communication channels were present having carrier frequencies in the range from 100 MHZ
; to 290 MHZ.
It will be readily apparent to those skilled in the art ' that a branched path, path routing arrangement in accordance with the present invention could be characterized by some other system of organization, for example, a binary based system of organization -e.g. 64 vertical platforms, each having 64 vertical transmission tracks; 64 horizontal platforms, each having 64 cross horizontal - 20 transmission tracks; and, for each possible pair of such platforms, 64 interconnecting front horizontal transmission tracks. Sixteen channels using part of the frequency spectrum between 20 MHZ and 220 ~Z could, for example, be adopted for use in conjunction with ;
such a system.
Also, as was discussed in the introductory portion of this specification, branched path, path routing arrangements which are not symmetric in their structure are contemplated.
Obviously, many modifications and variations in the present invention are possible in light of the foregoing teachings.
It is, therefore, to be understood that within the scope of the - appended claims, the invention may be practiced otherwise than as specifically described.
- 8~ -
9-7) on a 2 MHZ carrier, prospectively to open horizontal gate GHl 99 97. However, horizontal gate GHl 99 97 would already `
be open. It would not close in the absence of the required ~'~ 6000 HZ DISCONNECT tone. However, a transmission path would -` 'd ~ :
i exist between incoming line Iol25 and outgoing line 09997. 1 ~
. ~.
j- If the external equipment (not shown) to which line 09997 is connected is conditioned to recelve channel 1 LOW
i:'.'5 from line Iolol, attempted communications on channel 5 LOW
.. i; . .
`~i from line Iol25 would be heavily attenuated and would not .-J
interfere. However, the external equipment (not shown) to-which line Io125 is connected would presumably be conditioned ; to receive channel 7 HIGH from line ~9997 and would accordingly '` 30 receive communication intended to be directed only to line I
.. . . . .. . . . .. .
1~84183 Thus, it is preferable that the external equipment (not shown) associated with line ~9997 include means to detect the instance of access by line Iol25 and to send a signal back through the path routing arrangement to disable reception by the external equipment (not shown) associated with line I
of channel 7 HIGH.
This characteristic of unwanted access to other communications may be avoided by assigning channels in complete dependency on the last digit of the identifying number of the line. For example, channel numbers from an incoming line to path routing arrangement 1 as set forth in Table A may be fixed as indicated, but channel numbers from an outgoing line to path routing arrangement 1 would be variable depending on the channel number of the incoming line and not fixed depending on the last digit of the number identifying the outgoing line.
Thus, for example, incoming lines having as a last digit identi-fying the line the number N (ie. IwxyN) would provide communication s1gnals to the path routing arrangement 1 on channel N LOW ~ ' (N=0,1,.... ,9) and would always receive communication signals from the path routing arrangement on channel N HIGH (N=0,1,..... ,9).
Nescessarily, outgoing lines would then receive communications from the path routing arrangement on any of the LOW channels but would provide communications to the path routing arrangement on any of the ten HIGH channels in dependency on the incoming line with which it is linked. An advantageous consequence of this method of assignment is that it is no longer necessary to connect the BUSY LINES of every tenth horizontal transmission gate on the same front horizontal transmission track as was done with the previous method of channel assignment. If the BUSY LINES of every tenth vertical transmission gate are connected ( for example, the BUSY LINES of vertical gates V1,1,99' GVl,ll,gg, GVl,2l,99~ --~ GVl 91 99)~ then it is assured that no other incoming line that would dictate occupation ~-of the same two channels will gain access to the same front horizontal transmission track once access is gained by one such line. For example, if a bi-directional link was established between incoming line Iolol and outgoing line ~9997 in FIGURE 1 communications signals from line Iolol to line ~9997 would be-on channel 1 LOW. Communications signals in the opposite direction would be on channel 1 HIGH. Incoming lines Iol11, Iol21, Iol31, ..., Iolgl (not shown) would be denied access to front horizontal transmission track Fl 99. Any other incoming line on vertical platform VPl would have access to track F
and would have further access to any cross horizontal track ; connecting to track Fl 99 through a horizontal gate. Such further access would depend only on whether the horizontal gate was disabled by a busy signal from another gate on the same cross horizontal transmission track - the BUSY LINES of hori-zontal transmission gates in this respect being connected in f the same manner as for the previous method of channel assignment.
If it now occurred,for example, that there was an attempted link between incoming line Iol25 (not shown~ and out-going line ~9997 when a link between incoming line Iolol and ~utgoing line ~9997 was already established, then the communi-cation from line ~9997 intended to be directed only to line I
would not be received on the channel (channel 5 HIGH) which the external equipment (not shown) connected to line Io125 would be conditioned to receive.
However, as was discussed with respect to the previous method of channel assignment,it is still preferable that the external equipment (not shown) associated with each outgoing line such as line ~9997 include means to detect the instance of access by a second incoming line such as line Iol25 ~not shown) and to send back a signal to which the external equipment (not shown) of line Iol25 is responsive. The reason is to condition the external equipment associated with line Iol25 and prevent the generation by such equipment of the control signal sequence 5800 HZ - 5400 ~Z - 6000 HZ - t9-7-DIscoNNEcT) on a 2 MHZ carrier thereby causing horizontal transmission gate GHl 99 97 to close and break the link between line Iolol and line ~9997. Pre-ferably such conditioning signal would not prevent the generationof the control signal sequence 5800 HZ - 5800 HZ - 440C HZ -5000 HZ - 6000 HZ (9-9-2-5-DISCONNECT) required to close vertical transmission gate GVl 25 99~
The use of path routing arrangement 1 in a communication system will be now described with reference to FIGURE 8 which is a symbolic diagram illustrating certain basic aspects of a ~;
i communications system that interconnects a plurality of audio/~ideo - subscriber terminals T (To,Tl, ~ Tgggg) through an exchange 1 ;~
. ,, ~ .
;~. to enable bi-directional audio/video communications links to be established between calling ones and called ones of the ; subscriber terminals. Only two subscriber terminals Tj (PARTY A) , and Tk (PARTY B), and portions of the system associated immediately therewith are shown.
For purposes of illustration it will be assumed in particular instances that PARTY A is identified by the number "4828" and that PARTY B is identified by the number "8764".
With each subscriber terminal T (To,Tll ...,Tg999) there is associated line equipment E (Eo,El, ~Egggg) located within the exchange 1. Only line equipment Ej and Ek is shown.
'0 Terminal lines L (Lo,Ll ....,Lg999) which may, for example, be coaxial cable provide a bi-directional transmission path between the subscriber terminals T and their respective line equipment E - only lines Lj and Lk being shown.
In general, it is contemplated that subscriber terminals T may be remote from exchange 1 and accordingly a portion of each terminal line L is common with nine other such portions. Thus, in FIGURE 8, portion Ljp of 8 line Lj (i.e. the portion of line Lj between points 22 and 23 of line Lj) may be thought of as common with terminal line portions Ttj+l)p, ...., T(j+g)p.
Similarly, portion Lkp of line Lk may be thought of as common with prtin L(k+l)p' ~L(k+g)p; it being understood that the j-series of lines does not overlap with the k-series of lines.
Ten subscriber terminals T share the line portions because it is assumed, as with communications signals through the path routing arrangement, that up to 20 communication channels may occupy a ` terminal line. In particular, it will be assumed that each sub-' scriber terminal, depending on the last digit of its terminal number, transmits on a LOW channel in accordance with TABLE A
and receives on a corresponding HIGH channel in accordance with - 20 TABLE A. (For this purpose reference to "from an incoming line"
or "from an outgoing line" as appears in Table A should be ignored).
Thus, for example, PARTY A in FIGURE 8 (number 4828) transmits on channel 8 LOW (142 MHZ) and receives on channel 8 HIGH (Z42 MHZ).
Likewise, PARTY B (number 8764) transmits on channel 4 LOW (118 MHZ) and receives on channel 8 HIGH (218 MHZ).
The line equipment E of each subscriber terminal T is connected by two bi directional transmission paths (for example, coaxial lines) to the path routing arrangment 1 of FIGURE 8. As shown by the example of line equipment Ej and Ek, one such - 30 path is an incoming line Ij or Ik, as the case may be; the other 1~84183 such path is an outgoing line ~j or ~, as the case may be. The connectiOn of incoming and outgoing lines to the path routing arrangement was discussed with reference to FIGURES 2(a) and 2 (b). Also, the identification of incoming and outgoing lines ;
was discussed, but as can be seen in FIGURE 8 theidentification of a given incoming or outgoing line has been arranged to correspond with the identification of the subscriber terminal T with which it is associated.
The line equipment E of any subscriber terminal T has three basic modes of operation: (1) a calling mode of operation where the subscriber terminal with which it is associated is the terminal from which a call is placed; (2) a called mode of operation where the subscriber terminal with which it is associated ,1 ~
is the terminal to which a call is placed; and (3) a standby mode of operation in which the sbuscriber terminal is neither in the called or calling mode of operation. In the calling mode of ' operation the line equipment Ej, for example, provides circuit paths between the terminal line Lj and the incoming line Ij for for communications from the calling subscriber terminal to the called subscriber terminal, and for communications from the called subscriber terminal to the calling subscriber terminal.
In the called mode of operation similar circuit paths are pro-vided between the terminal line Lj and theoutgoing line ~
The line equipment E also provides control signals to control the operation ofthe transmission gates in path routing arrangement 1 of FIGURE 8. In the description that follows it is assumed that such control signals are provided over the incoming lines associated with calling subscriber terminals rather than over separate circuit lines from the line equipment to the gates. Generally, using by way of example the particular sub-~L~84183 scriber terminals shown in FIGURE 8, the line equipment operates as follows: On a call from PARTY A to PARTY B, the line equipment Ej of PARTY A, starting from its standby mode of operation is first "seized" by an appropriate command from sub-scriber terminal Tj which seizure switches line equipment Ej to the calling mode of operation. The line equipment Ej is then conditioned to receive further commands from the subscriber terminal ,, ~
Tj and in response thereto to provide selected code signals over ~ incoming line Ij to open the desired gates in the path routing -!- arrangement. On a call from PARTY A to PARTY B, and assuming access can be gained to all necessary transmission tracks (i.e.
no BUSY SIGNALS), such control signals are coded to open vertical transmission gate GV48 28 87 and horizontal transmission gate GH48 87 64 thereby defining a transmission path including these gates through path routing arrangement 1 between incoming line Ij and outgoing line ~k If the call had been from PARTY B to PARTY A, g Gv87~64~48 and GH87,47 28 would have been opened and the defined transmission path would have been between incoming line Ik and outgoing line Referring to path routing arrangement 1 as shown in FIGURE 8, it will be appreciated that with the exception of vertical transmission tracks V48,28 and V87,64, appearing within the arrangement roughly approximates the geometric locations of the two possible paths between PARTY A and PARTY B
in the three dimensional structure of FIGURE 1. The x-z axes in FIGURE 8 correspond to the x-z axes shown in FIGURE 1. For example, in FIGURE 8 front horizontal transmission track F48 87 is approximately where it should be (although its width is greatly exaggerated) considering that it is on the 49th vertical platform (not shown) of 100 vertical platforms (not shown) 1~8418-3 stacked in vertical stack 8 between side walls 7b and 7a - the first such platform being adjacent side wall 7b.
Of course, the particular design of line equipment ; will depend upon a number of factors including: the character of control signals the line equipment receives from the sub-scriber terminal; the character of control signals the line equip-ment must provide to operate the transmission gates of the path routing arrangement and the means whereby such control signals are transmitted to the transmission gates (i.e. as an input to the path routing arran~ement from incoming lines, or, as an input to the path routing arrangement on control signal lines . . - .
separate from the licensing lines); the conditioning action that the line equipment is required to perform on communications sig-nals to maintain proper frequency division of channels; and, the character of control signals the line equipment receives from or ~3 sends to other line equipment.
With regard to the maintenance of proper frequency division, it will be appreciated that,depending on channel ~-assignmentsthrough the path routing arrangement, and depending on the receiving and transmitting channels of the ~subscriber terminal, the line equipment of a particular subscriber terminal may be required to translate the carrier frequency of communica-tions signals it receives from the subscriber terminal, or from its associated incoming or outgoing line. FIGURE 8 (a) shows a number of possible channel assignments that maintain a division of frequency along various portions of the transmission path between PARTY A and PARTY B when PARTY A is the calling party. Path routing arrangement 1 is shown superficially in FIGURE 8 (a) because it is assumed that the communications link therethrough is established.
1o84l83 ` In FIGURE 8 (a), carrier frequencies along various portions in a glven direction of transmission (as indicated by ~ .
the arrows) are indicated generally by fA~ fA~ fB and fB for . each of four methods of channel assignment. The particular ~ :
channels that would be occupied along each portion of PARTY A
. and PARTY B were identified by the numbers "4828" and "8764", ; respectively, is indicated in brackets beneath the generally ~` indicated carrier frequencies. As can be seen, irrespective of ~:~ the method of channel assignment, PARTY A always transmits on the carrier frequency fA (8LOW) and receives on the carrier frequency fA (8 HIGH), and, PARTY B always transmits on the carrier frequency fB (4 LOW) and receives on the carrier frequency fB (4 HIGH). Also, it can be seen that irrespective of the method of channel assignment, a division of frequency is maintained ~.
over the path through the path routing arrangement 1 included in portion 2.
j The first and fourth methods of channel assignment shown in FIGURE 8 (a) have been previously discussed in the limited context of path routing arrangement 1 per se.
' 20 As indicated by the first method, the channel which is occupied for transmission from incoming line Ij (I4828) to g g ~k (~8764) is determined by the last digit identifying the incoming line Ij and is a LOW channel (8 LOW~; and the channel which is occupied for transmission from outgoing line ~k to incoming line Ij is determined by the last digit identifying the outgoing line ~k and is a HIGH channel (4 HIGH). According to the first method, it can be seen that line equipment Ej in the calling mode of operation is not required.to translate the carrier frequency fA of signals it receives from line Lj because the carrier frequency at its output to line Ij is the same.
1084~83 ., However, line equipment Ej may be required to translate the carrier frequency fB of signals received from line Ij because the carrier frequency fA at its output to line Lj is not ~ necessarily the same. For the example shown, frequency translation is clearly required to convert channel 4 HIGH to channel 8 HIGH, but would not be required if the number of PARTY B had been, for example, "8768". Also, according to the first method of channel assignment, it can be seen that the line equipment j Ek in the called mode of operation is required to translate carrier frequency in both directions of transmission - to convert ; a LOW channel to a HIGH channel for signals received fr~m line ~k and to convert a LOW channel to a HIGH channel for signals received from line Lk.
In the fourth method of channel assignment shown in FIGURE 8 (a) it can be seen that the channels occupied in path routing arrangement 1 are completely determined by the last digit identifying the incoming line. Consequently, as can be seen, line equipment Ej in the calling mode of operation is not required to translate carrier frequencies in either direction of transmission, but, line equipment Ek in the called mode of operation is required to translate carrier frequencies -;-in both directions of transmission.
The second and third methods of channel assignment shown in FIGURE 8 (a) service to indicate that other methods of channel assignment are possible. However, these additional methods certainly do not exhaust the possibilities.
Moreover, it might be noted that it is not necessary that the fre-quency bands occupied by the twenty possible channels that may, in general be carried over a terminal line L (portions 1 and 3 in FIGURE 8 (a)) do not necessarily have to be the 1~34183 same frequency bands occupied by the 20 possible channels in a defined path through path routing arrangement 1 (portion 2 in FIGURE 8 (a) - although there would of course be a correspondence between frequency bands. For example, in method 1 shown in FIGURE 8 (a), the carrier frequencies in portion 2 could theoretically be for example 1.5 fA and 1.5 fB ' or for example, fA + 50 MHZ and fB + 75 MHZ, rather than fA and fB, respectively, as indicated.
For some methods of channel assignment, the system must include means whereby the line equipment of a calling subscriber terminal can condition the line equipment of a called subscriber terminal to transmit to the calling subscriber terminal on a desired carrier frequency. For example, referring to method 4 in FIGURE 8(a), it can be seen that line equipment E~
receiving channel 4 LOW on line Lk is required to transmit on ; channel 8 HIGH to line k In general, line equipment Ek in the called mode of operation for method 4 may be required to transmit on any of 10 HIGH channels but cannot "know" which HIGH channel absent some identification from the calling party.
Where a requirement for such identification arises, it is contemplated that the line equipment of a calling party, in addition to providing control signals to define a path through the path routing arrangement, will also provide a control signal to the line equipment of the called party which latter control signal identifies the calling party. Such identifying control signal may, for example, be an audio tone in accordance with Table B superimposed on, for example, a 3 MHZ carrier signal -such audio tone being a "home tone" representing the channel number (the distinction between HIGH and LOW channels not being a matter for concern) of the calling party. The line equipment i. ` 1~4183 ,. .
of the called party, receiving the "home tone" on a 3 MHZ carrier - would include channel selection means responsive to the home ~- tone to select the carrier frequency on which the line equipment of the called party transmits to its outgoing line. Thus, for example line equipment Ej would transmit a 5600 HZ (Channel 8) home tone on a 3 MHZ carrier to line equipment Ek over the defined path from Ej to Ek causing line equipment Ek to transmit to line .
~k on channel 8 HIGH.
The same principles of "home tone" control may be used to tune a receiver in the line equipment ofa called party to ~.
receive a desired channel. For example, referring to method 1 or method 4 in FIGURE 8(a), a 5600 HZ (Channel 8) home tone on a 3 MHZ carrier could be used to tune a receiver in line equipment Ek to receive channel 8 LOW.
Once having decided on the desiredperformance of a system such as is shown in FIGURE 8 and having regard to the characteristics of the transmission gates and the character of control and communication signals from the subscriber terminals, then the design of line equipment to achieve the desired system response will be a routine matter to those skilled in the art.
As an illustration of one embodiment for line equipment, a communications system wherein channel assignments are in accor-dance with the first method of channel assignment shown in FIGURE
8(a) will now be considered with reference to FIGURES 9 to 11. A
number of assumptions will be made, and they are as follows:
(a) The transmission gates used in the path routing arrangement are of the type shown in FIGURE 7. All the ~:
BUSY LINES 109 (not shown in FIGURE 7 but see discussion relating FIGURE 7 to FIGURE 5) of vertical transmission gates on a given front horizontal transmission track are connected to each other and all BUSY LINES 109 of horizontal transmission gates on a given cross horizontal transmission track are connected to each other.
(b) Carrier frequencies transmitted from a subscriber terminal correspond, as previously discussed, to the last digit identifying the subscriber terminal. The first six megahertz of baseband is assigned to carrier video and the 7.5 MHZ baseband frequency for each channel is used as a subcarrier for audio.
(c) Audio intelligence tie. voice frequency) appears below 4 KHZ audio control signals appear out of band at or above 4 KHZ in accordance with TABLE B. Audio digit tones -~
(0 to 9) are produced by a subscriber terminal in response, for example, to the manual depression of a desired digit button on the subscriber terminal. In addition, a 6000 HZ DISCONNECT tone is produced by a subscriber terminal in response, for example, to hanging up a receiver of the subscriber terminal. Further, a 6200 HZ SEIZURE tone is produced by a subscriber terminal in response, for example, to picking up the receiver of the audio terminal.
(d) The line equipment is line equipment Ej for PARTY A
(No. 4828) in FIGURE 8. The lines Lj, Ij and Oj shown in FIGURE 9 thus correspond to the lines Lj, I j and Oj shown in FIGURE 8.
Accordingly, signals arrive on line Lj on a 170 MHZ
carrier (channel 8 LOW), and signals leaving on line Lj leave on a 270 MHZ carrier (channel 8 HIGH). In the calling mode of operation, communications signals leaving on line Ij leave on a 170 MHZ carrier (channel 8 LOW) and communications signals arriving on line Ij arrive on a carrier within the band from - 1~)84183 : ,:
; 200 MHZ to 300 MHZ (one of the channels 0 to 9 HIGH). In the called mode of operation communicationS signals arriving on line Oj arrive on a carrier within the band from 100 MHZ to 200 MHZ
(one of channels 0 to 9 LOW) and communications signals leaving ~ -on line Oj leave on a 270 MHZ carrier (channel 8 HIGH).
The operation of line equipment Ej in FIGURE 9 will first be considered assuming it is initially in the standby mode of operation, then switches to the calling mode of operation on a call to PARTY B (No. 8764) and then switches back to the standby mode of operation. The operation will then be considered assuming the line equipment is initially in the standby mode of operation, then switches to the called mode of operation, and then switches back to the standby mode of operation. In both cases reference will be made from time to time to FIGURES 10 and 11 which show elements of FIGURE 9 in greater detail.
(1) Standby-Calling-Standby Before line equipment Ej can provide control signals to line Ij to open the necessary gates in the path routing arrangement (not shown in FIGURE 9) to define a path to PARTY B and su~-sequently allow PARTY A to communicate with PARTY B, normallyopen switch SW must first be closed. In the standby mode of operation, this switch is open, but closes in response to a logical 1 input on line 522 from output c' of calling control circuit. As Will be seen, both control signals and communications signals provided to line Ij from line equipment Ej must pass through switch SWa.
Line equipment Ej will cause closure of switch SW if it is in the standby mode of operation and receives at its input from line Lj a 6200 HZ seizure tone on a 7.5 MHZ subcarrier in channel 8 LOW. All signals appearing on line Lj as an input 1~84183 , .
s to hybrid Hl appear at the output of hybrid Hl on line 500 to the input of channel filter 501. Channel filter 501 is a bandpass filter which passes only channel 8 LOW and blocks the other 9 LOW channels that may appear on line Lj as a result of the sharing of a portion of line Lj with other subscriber terminals. Likewise, channel filter 501 blocks all 9 HIGH
channels which appear on line Lj (ie. excluding 8 HIGH).
Assuming hybrid Hl is ideally balanced, channel 8 HIGH would not appear on line 500, but, if there is some unbalance, channel filter 501 blocks the signal.
Signals appearing within channel 8 LOW at the input of channel filter 501 appear at the output thereof on line 502 to the input of hybrid H2 which provides the input signal as an output to lines 503 and 504, still within channel 8. The output signal from hybrid H2 on line 503 is also the input to line receiver 505 which receives channel 8 and produces as an output on line 506 the baseband signal (0-6 MHZ video and 7.5 MHZ audio subcarrier). The baseband signal is passed through hybrid H3 which provides the baseband input on line 506 as an output on lines 507 and 508. The output on line 508 will not be considered for the moment because, as will be seen, it is only used when line equipment Ej is in the called mode of operation.
The ouput on line 507 is the input to input "a" of calling control circuit 509.
Calling control circuit 509 is a multi-function element shown in greater detail in FIGURE 10. In addition to controlling the operation of switch SWa, it also ensures that digit tones are provided to the path routing arrangement on the proper carrier frequencies (1 MHZ or 2 MHZ as the case may be). Additional functions that are preformed will be described as the description proceeds.
i~84183 Referring now to FIGURE 10, when a baseband signal appears on line 507, it is first filtered by high pass filter l9S
which removes the video component (0-6 MHZ) of the baseband signal, allowing only the audio subcarrier (7.5 MHZ) to pass to line 196.
Receiver 197 is a 7.5 M~Z receiver which receives the audio subcarrier on line 196 and produces at its output on line 198 audio intelligence (voice frequencyl plus audio control (out-of-band --4KHZ and above). High pass filter l9g removes the voice frequency range of the audio signal and passes only the out-of-band range to its output on line 200.
The remainder of calling control circuit 509 processesthe various audio control signals that may appear on line 200.
; The element which determines whether or not line equipment Ej is in the calling mode of operation is flip-flop FFS. Normally, its output on line 522 is logical 0. Consequently switch SW : -is FIGURE 9 will be open meaning that line equipment Ej is either in the standby mode of operation or the called mode of operation. The output of flip-flop FFS on line 522 will be switched to logical 1 if a 6200 HZ SEIZURE tone appears on line 200 provided line equipment Ej is not in the called mode of operation.
When a SEIZURE tone appears on line 200 it also appears on line 200a to the input of receiver detector R/DS which is tuned to receive and detect 6200 HZ. A 6200 HZ tone input causes the output of receiver detector R/DS on line 205 to switch to logical 1 which output is also one input of dual input logical AND gate ANDS. If the other input to gate ANDS from line 526 is also logical 1, the output of gate ANDS on line 206 to logical inverter INVS will follow the output of receiver detector R/DS
.30 on line 205. Then, the output of inverter INvs ~n line 207 to :
1~84183 the set input of flip-flop FFS will switch to logical 0 when the output of receiver detector R/DS, in response to a SEIZURE tone, switches to logical 1. At the termination of the SEIZURE tone, ; the output of inverter INVS switches from logical 0 to logical 1 thus providing a set command to flip-flop FFS causing output PS
to line 522 to switch to logical 1 from logical 0. Switch SWa in FIGURE 9 will then close and line equipment Ej is in the calling mode of operation.
As can be seen by referring to FIGURE 9, line 526 which is one input of gate ANDS in FIGURE 10, receives signals from output 'c' of called control ciruit 538. When line equipment Ej is in the called mode of operation, the signal at ouput c' of called control circuit 538 is logical 0 (the means will be discussed in more detail hereinafter with reference to FIGURE 11) which disables gate AND5 to prevent a seizure tone from providing a set command to flip-flop FFS. Nevertheless, a SEIZURE tone will be detected by receiver detector R/DS even if line equipment Ej is in the called mode of operation. As can be seen in FIGURE 10, the output of receiver detector R/DS on line 205 also appears as an output to line 525. Line 525, as can be seen from FIGURE 9, provides an input to input b of called control circuit 538. The response of called control circuit 538 to logical signals appearing on line 525 is of concern in the called mode of operation only and will be considered later.
Referring again to FIGURE 10, it can be seen that calling control circuit 509 includes four digit tone stages DTSl, DTS2, DTS3 and DTS4, only the first digit tone stage DTSl being shown in detail. The structure of each stage is identical the first, -each having three inputs al, a2 and a3, and four outputs a4, a5, a6 and a7. As can be seen, the output a4 is only used for 1~84183 ::
the first staye DTSl and the outputs a6, a7 are not used for the fourth stage DTS4. Each stage includes a receiver detector R/DT
which is widely tuned to switch to logical 1 if the signal appearing .
at its input (on line 225 for stage DTSl) is any of the 10 digit :
tones from 4000 HZ to 5800 HZ. Referring to stage DTSl by way of example, when the output of receiver detector R/DT on line 226 to the input of logical inverter INVT switches to logical 1, then the output of inverter INVT on line 227 to set input ST of ~.
flip-flop FFT switches to logical 0. The output of INVT switches back to logical 1 at the terminatlon of a tone detected by receiver detector R/DT thus providing a set command to flip-flop : -S ' -~
In the standby mode of operation, the output PT
of each flip-flop FFT is of all stages logical 0. These outputs sequentially switch from logical 0 to logical 1 at the termination of each successive digit tone. Such sequential control is determined by the sequential switching of normally open switch SWT of each digit tone stage 1 which switch closes in response to a logical 1 control input (on line 222 for stage DTSl) from dual input logical AND gate ANDT f each stage.
- Referring to stage DTSl it can be seen that one input of gate :
ANDT appears on line 220 from input a3 of stage DTSl; the other .
input appears on line 221 from complementary output PT of flip-flop FFT via line 229 from output PT. Complementary output PT
is the inverse of output PT: if PT=0, then PT-l; if PT=l, then PT=0. Thus, gate ~NDT is closed when the input to input a3 is logical 1 and the output PT of flip-flop FFT is logical 1.
Since the output PT of each flip-flop FFT is logical 0 in the standby mode of operation, the output PT of each flip-flop FFT will be logical 1. With the exception of stage DTSl, the input a3 of each stage will be at logical 0 in the standby mode of operation because this input is the output a6 of the previous stage (via lines 235, 237, 239 as the case may be) which output is taken from output PT of flip-flop FFT in each stage (ie.
via line 228 in stage DTSl). The input a3 of stage DTSl is connected to the output PS of flip-flop FFS by line 222 and the line to line 522 and is thus logical 0 when line equipment Ej is in the standby mode of operation.
As has been ~escribed, when line equipment Ej switches to the calling mode of operation at the end of a SEIZURE tone, ; the output PS of flip-flop FFS is logical 1. Then, the input a3 of stage DTSl becomes logical 1. Since output PT of flip-flop ; FPT in stage Dl'Sl is also logical 1, gate ANDT produces a logical 1 output on line 222 causing switch SWT in stage 1 to close. The first digit tone that appears on line 200 and, through low pass filter 201, on line 203, (which tone would be ` 5600 HZ - the digit 8 - on a call from PARTY A to PARTY B) also appears as an input on line 200c to input al of stage DTSl and is passed over line 224 and through switch SWT which switch is now closed to line 225. So long as the tone appears ~n line 225 it also appears via line 231 at output a5 of stage DTSl.
When the first digit tone terminates, the output PT
of flip-flop FFT in stage DTSl switches to logical 1 and output T f flip-flop FFT in stage DTSl switches to logical 0. The logical 0 condition of output PT causes switch SWT in stage DTS
to open. The logical l-condition of output PT off flip-flop FFT in stage DTSl which condition appears at input a3 of stage DTS2 causes switch SWT in stage DTS2 to close because the output PT of flip-flop FFT in stage DTS2 is also logical 1. Stage DTS2 responds to the second digit tone that appears on line 203 (which tone would be 5400 ~Z - the digit 7 - on a call from PARTY
A to PARTY B) in the same manner that stage DTSl responded to the first tone. During the continuance of the second tone at input al of stage DTS2, the same tone would appear at output a5 of stage DTS2. In the same manner, the next two digit tones (5200 HZ-4800 HZ the digits 6-4) would appear sequentially at outputs a5 of stages DTS3 and DTS4 respectively.
When a tone appears at an output a5 of one of the ' digit tones stages of FIGURE 10 it is directed through either amplifier AMPa to line 511 or amplifier AMPb to line 512 which lines are, respectively, inputs to the 1 MHZ and 2 MHZ modulators shown in FIGURE 9. As can be seen in FIGURE 10, each amplifier has three inputs, one input of which derives in each case from the output of disconnect filter 202. The other two inputs to amplifier AMPa are from output a5 of stage DTSl on line 233 and output a5 of stage DTS2 on line 240. The other two inputs to amplifier AMPb are from output a5 of stage DTS3 on line 241 and output a5 of stage DTS4 on line 242.
Both amplifiers AMPa and AM2b operate as summing amplifiers producing at their outputs the tone that appears at one of their three inputs. The input impedance of each input to the amplifiers should be sufficiently high to avoid having a signal on one input line appear on another input line of the same amplifier with sufficient power to be detected by the receiver detector associated with the other input line. Otherwise, for example, the output PT of flip-flop FFT of stage DTS2 could be switched to logical 1 at the termination of the first tone.
Then, switches SWT in stages DTS2 and DTS3 would he closed when the second digit tone appeared and the sequential operation would be destroyed. Alternatively, any tendency for this result to i~S4~83 occur will be suppressed by the insertion of buffer amplifiers on each of lines 215, 233, 240, 241 and 242.
Assuming then that such irregular operation does not occur, the first two digit tones that appear in sequence on line 203 will also appear in sequence at the output of amplifier AMPa to line 511, or, as shown in FIGURE 9, at output a'of calling control circuit 509. Likewise, the next two digit tones that appear in sequence on line 203 will also appear in sequence at the output of amplifier AMPb to line 512, or, as shown in FIGURE 9, at output b' of calling control circuit 509.
Referring now to FIGURE 9, the tones appearing on line 511 are the modulating input to modulator MODl, the output of which modulator is a 1 MHZ carrier on line 513 to hybrid H7 - the carrier being modulated by the modulating input. Hybrid H7 produces at its output on line 515 the signals that appear on lines 513 and 514. The signal that appears on line 514 is a 2 MHZ carrier from modulator MOD2 which carrier is modulated by tones appearing at the input to modulator MOD2 on line 512.
The 1 MHZ and 2 MHZ modulated carrier signals are combined by hybrid H8 with the channel 8 LOW signal appearing on line 504. Thus, the combined channel 8 LOW signal and mod-ulated 1 MHZ and 2 MHZ carrier signals appear at the output of hybrid H8. Switch SWa which is now closed passes the combined signals to the input of line amplifier AMPl. From the output of amplifier AMPl the combined signals appear on line 518 to the input of hybrid Hg which hybrid provides the output of line equipment Ej to line Ij.
The sequence of tones appearing on the 1 MHZ and 2 MHZ
carriers will first cause vertical transmission gate GV48 28 87 (see FIGURE 8) to open and then cause horizontal transmission 1~84183 gate GH48 87 64 (see FIGURE 8) to open - assuming that the gatcs are generally as shown in FIGURE 7 and assuming th.at the gates are not disabled by busy signals. If the gates were disabled, then of course a path to PARTY B would not be established.
FIGURE 9 does not show means that would aetect that a path has not been established - ie. there is no provision for a busy signal.
FIGURE 9 does show a meanstoprovide a dial tone indicating that line equipment Ej has switched to the calling mode of operation. When the output e' of calling control circuit 509 is logical 1, normally open switch SWc is caused to close allowing a dial tone appearing on a 7.5 MHZ audio subcarrier line 528 at the output of dial tone generator 527 to pass through switch SWc to the input of hybrid H5 on line 529. The dial tone per se may ~e any audible frequency or frequencies attractive to the human ear. The 7.5 MHZ modulated subcarrier signal appears at the output of hybrid H5 on line 533 to the input of hybrid H4, and then at the output of hybrid H4 on line 545 to the input of line transmitter 546. Inputs to line transmitter 546 are transmitted at its output to line 547 on the 270 MHZ
channel 8 ~IGH carrier frequency required for reception by the subscriber terminal of PARTY A. The line transmitter output on line 547 is amplified by line ~lP3 and appears as the input to hybrid Hl on line 548 which hybrid provides the output on line Lj to subscriber terminal Tj (not shown in FIGURE 9.) Referring to FIGURE 10, it can be seen that a logical 1 condition on line 524 to switch SWc in FIGURE 9 will only appear so long as the output of dual input logical AND gate 210 is logical 1. The output of gate 210 is logical 1 only if the input thereto on line 210 from the output PS of flip-flop FFS tvia 1~84~
the line "to line 522") is logical 1 and if the input thereto on line 232 from output a4 of stage DTSl is logical 1. It may readily be concluded that a dial tone will last from the time line equipment Ej switches to the calling mode of operation and until the termination of the first digit tone.
Assuming ~hat a bi-directional communications link is established between PARTY A and PARTY B, communications signals from PARTY B appearing at the input of hybrid Hg from line Ij will appear at the output of hybrid Hg on line 530 to front wall receiver 531. Since in general such communications signals may occupy any one of ten HIGH channels, and since line equipment E
shown in FIGURE 9 does not include means to ;automatically tune front wall receiver 531 for the channel it will receive, then, the receiver 531 must be widely tuned to receive any of the 10 HIGH channels.
The output of front wall receiver 531 on line 532 to hybrid H5 is the baseband (0-6 MHZ video and 7.5 MHZ audio subcarrier) of the channel being received. From the output of hybrid H5 on line 533, the baseband signal follows the same path and undergoes the same conditioning as was described for the 7.5 MHZ dial tone subcarrier. The baseband signal is transmitted to subscriber terminal Tj (not shown in FIGURE 9) on channel 8 HIGH.
It is thusapparent that, in the calling mode of operationand except when the input from line Ij is channel 8 HIGH, communication signals passing through line equipment Ej from line Ij to line Lj undergo carrier frequency translation as a result of the combined effect of front wall receiver 531 and line transmitter 546.
; 30 Line equipment Ej shown in FIGURE 9 switches from the calling mode of operation back to the standby mode of operation 8 ~
in response to a 6200 DISCONNECT tone appearing on the proper subcarrier and carrier frequencies as an input on line Lj. When such tone appears it detected by calling control circuit 509 in much the same manner as other audio control signals. Referring to FIGURE 10, a tone appearing at the input of disconnect filter 202 on line 200b will appear at the output of filter 202 if it is a 6000 HZ DISCONNECT tone. This filter is a band pass filter sharply tuned to block control tones other than 6000 HZ.
Receiver detector R/Dd receives the output of filter 202 on `
line 212 and switches to logical 1 at its output on line 213 if a DISCONNECT tone appears at its input. (Because of the filtering action of filter 202 it is not necessary that receiver detector R/Dd be sharply tuned for 6000 HZ). Through logical inverter INVd and line 214 to reset input RS of flip-flop FFS, flip-flop FFS is reset to its standby mode condition at the termination , ~
of a disconnect tone. Likewise, flip-flops FFT in stages $
DTSl to DTS4 receive, via lines 216, 234, 236 and 238, reset commands at their inputs RT at the same time.
As can be seen, any DISCONNECT tone that appears at the output of disconnect filter 202 on line 212 becomes ~n input~
(via lines 215 and 219) to both amplifiers AMPa and AMPb -in the result modulating both the 1 MHZ and 2 MHZ carrier signals being transmitted to the line equipment on line Ij. At the termination of the DISCONNECT tone on the 1 MHZ and 2 MHZ carriers, the open transmission gates in the path routing arrangement on the path between PARTY A and PARTY B are caused to close.
The purpose of low pass filter 201 can now be seen.
In passing only audio control signals below 6000 HZ, filter 201 does not allow a DISCONNECT tone to operate the receiver detectors R/DT associated with flips-flops FFT in the stages DTSl to DTS4.
~ ':
1~8418~ -Otherwise, unless such receiver detectors were designed not to respond to the 6000 HZ DISCONNECT tone, a flip-flop FFT might receive a set command and a reset command at the same time.
This situation would arise where a DISCONNECT tone was received before a digit tone sequence was complete. One of the switches SWT would be closed meaning that its corresponding receiver detector R/DT would detect the DISCONNECT tone at the same time as receiver detector R/Dd. An alternative way to control this situation would be to insert a time delay in line 216 - for example, two logical inverters connected in series.
(2) Standby-Ca_led-Standby Ordinarily, line equipment Ej switches from the standby mode of operation to the called mode of operation on detection of a 2 MHZ carrier signal input from line ~j to Hlo. The one exception is where the condition on line 523 from line 522 to input c of called control circuit 538 is logical 1 meaning that PARTY A must have called his own number.
The 2 MHZ carrier is detected by called control circuit 538 receiving its input at input a from hybrid Hlo - 20 via lines 534 and 535. As can be seen in FIGURE 11, the input to called control circuit 538 from line 535 is received by receiver detector R/DC which receiver is tuned to 2 MHZ and produces a logical 1 output on line 600 whenever a 2 MHZ signal is detected. Line 600 is one input of dual input AND gate ANDC, the output of which gate on line 602 switches to logical 1 if the input on line 601 from logical inverter INVC is logical 1 ` when a 2 M~Z signal is detected. The output of inverter INV
will be logical provided its input on line 523 is logical 0 (ie.
if A has not called his own number). When the condition on line 602 switches to logical 1, three events occur. Firstly, flip-,,~
~ -69-1~84183 flop FFC is set by the logical 0 to logical 1 transition occuring at its inpu-t Sc. Accordingly, the output to line 540 from output Pc of flip-flop FFC switch to logical 1. The logical 1 condition on line 540 closes normally open switch SWd which :~ :
allows signals appearing at the output of ring tone generator 541 on line 542 to pass through switch SWd to the input of hybrid H6 on line 543. As in the case of dial tone generator 527, ring tone generator produces audibly attractive ring tones on a 7.5 -MHZ audio subcarrier for ultimate reception by subscriber terminal L0 Tj. The input to hybrid H6 on line 543 appears at the output of ;
- hybrid H6 on line 544 to the input of hybrid H4 from the output ~, of which, on line 545, the signal follows the same path and undergoes the same conditioning as inputs to hybrid H4 from line 533. The ring tone terminates when flip-flop FFC in FIGURE 11 ~.
receives a reset command at input Rc from line 605 through logical OR gate ORC from line 525. As can be seen from FIGURE 10 I a reset command will be provided to line 525 when receiver detector R/DS detects a SEIZURE tone (ie. when the receiver at subscriber terminal Tj is picked up).
At the same time that output Pc of flip-flop FF
in FIGURE 11 switches to logical 1, the output of logical ; inverter INVc, receiving its input on line 603 from line 602, switches to logical 0. The logical 0 condition appears on line 526. As can be seen in FIGURE 10, a logical 0 condition on line 526 disables gate ANDS so that a SEIZURE tone cannot now cause - r a set command to appear at input Ss of flip-flop FFS.
. Finally, when the condition on line 602 is logical 1, the output to line 539 from line 603 is also logical 1. The logical 1 condition on line 539 (from output a' of called control circuit 538 to switch SWb in FIGURE 9) causes normally open switch SWb to close thereby completing a transmission path from the output of hybrid H3 on line 508 to line 0j. As will be recalled, the signal on line 508 will be the baseband components of channel 8 LOW. These components are received from line 508 by back wall transmitter 510 and transmitted to line 519 on the 270 MHZ carrier for channel 8 HIGH. rrhe signal on line 519 ;
passes through switch SWb, now closed, to the input of line amplifier AMP2 from line 520. The output of line amplifier AMP
on line 521 appears at the input of hybrid Hlo on line 521, which hybrid provides the output on line ~j to the calling party.
Signals received from line 0j appear on line 534 at the input of back wall receiver 536 as well as the input of -~
called control circuit 538. Since back wall receiver 536 may be required to receive any of 10 LOW channels and since the line equipment does not include channel selection means to automatically tune the receiver tc receive particular channels, it must be broadly tuned to receive any of the ten LOW channels.
The output of backwall receiver 536 on line 537 to hybrid H6 is the baseband component of the channel at the output of hybrid Hlo on line 534 from the output of hybrid H6 on line 544, the baseband signals will follow the same path and undergo the same conditioning as signals from ring tone generator 541.
In the called mode of operation, it is thus apparent that communicatlons signals passing through line equipment Ej, either from line Lj to line ~j, or from line ~j to line Lj, will-- -s undergo carrier frequency translation. Channel 8 LOW received on line Lj is converted to channel 8 HIGH by the combined effect of line receiver 505 and back wall transmitter 510. Any channel (which channel will be a LOW channel) received on line ~j will 1~84~83 ~e converted to channel 8 HIGH by the combined effect of back wall receiver 536 and line transmitter 546.
As can be concluded from FIGURE 11, the called mode of operation for line equipment Ej in FIGURE 9 will endure only so long as a 2 M~Z signal is detected by receiver detector R/DC.
The 2 MHZ signal is of course the 2 MHZ carrier from modulator -~
MOD2 of the calling party's line equipment and will terminate when the calling party causes a DISCONNECT tone to be produced.
The transmission gates in the path routing arranqement are then caused to open breaking the path for the 2 MHZ carrier from the calling party to the called party. The output from the circuit of FIGURE 11 to line 526 returns to logical 1; the output to line 539 returns to logical 0; and since flip-flop FFC was previously reset when PARTY picked up his receiver, the line equipment E
has now returned to the standby mode of operation.
It may occur on a call to PARTY A that PARTY A will not pick up his receiver to generate the SEIZURE tone necessary to reset flip-flop FFC in FIGURE 11. Accordingly, one-shot multivibrator /Sc is included in called control circuit 538 to produce a reset pulse whenever receiver detector R/DC
switch from logical 1 to logical 0. Thus, when a negative ~ r switching transition from logical 0 to logical 1 appears on line 600 one shot multivibrator /Sc produces a logical 1 pulse at its output on line 604 to gate ORC. The same pulse ~ appears at the output on line 604 to gate ORC. The same pulse -~ appears at the output of gate ORC on line 605 to reset input Rc of flip-flop FFC. The logical 0 to logical 1 switching transition on the leading edge of the pulse causes flip-flop FFC to be reset. Hence, if PARTY A does not pick up his receiver, calling control circuit 538 will nevertheless be . . ..
1~84~83 returned to its initial condition at the termination of a 2 ~HZ input detected by R/DC. Line equipment Ej will then be in the standby mode of operation.
(3) General There are some additional observations that might be made regarding line equipment Ej in FIGURE 9.
Firstly, it will now be apparent that certain elements of FIGURE 9 are only operative depending on the mode of operation.
For example, back wall transmitter 510 and back wall receiver 536 are only operative in the called mode of operation. Front wall receiver 531 is only operative in the calling mode of operation.
Line transmitter 546 is operative in the called mode of operation or the calling mode of operation. Line receiver 505, however, is operative in all three modes of operation - standby, calling, and called. Although not shown in FIGURE 9, it would of course be a simple matter to include means to switch such transmitters or receivers on or off, as required, depending on the mode of operation. A logical 1 signal is available as a control signal on line 522 in the calling mode of operation and a logical 1 signal is available on line 539 in the called mode of operation.
Secondly, as has been said, in the absence of means to automatically tune front wall receiver 531 and back wall receiver 536, such receivers must be widely tuned to receive any of 10 HIGH channels (in the case of receiver 531) or any of 10 LOW channels (in the case of receiver 536). Such wide tuning may cause undesirable noise in the system. Also, from earlier ~~
discussions, it will be recalled that it is contemplated that some embodiments of line equipment (then referred to as "external equipment") will be conditioned to receive particular channels to avoid interference when a front horizontal trans-mission track forms a part of the bi-directional link between ~84183 more than one pair of incomin~ and outgoing lines. (The latter situation does not arise where the line equipment is as shown in EIGURE 9 and the transmission gates are as shown in FIGURE 7 with ~he BUSY LINES of such gates connected in the manner aforesaid, but, whatever the reason for conditioning receivers to receive particular channels, the means in general may be the same).
With regard to FIGURE 9, it is evident that line equipment Ej will in all cases "know" in advance what channel will be received on line Ij from a called party. For example, when PARTY A calls PARTY B (No. 8764), it is known that the channel that will be received from incoming line Ij will be channel 4 HIGH. The "knowledge" as such may derive from output a5 of digit tone stage DTS4 of calling control circuit 509.
Such output is the digit tone corresponding to the last digit of the number of a called party. Where PARTY A calls PARTY B
the tone at output a5 would be 4800 HZ, representing the digit 4. I f FIGURE 12 illustrates how the tone appearing at ¦
output a5 of stage DTS4 may be used to condition line equipment Ej to receive a particular channel from incoming line Ij. Since ~20 the elements are very similar to elements previously described FIGURE 12 will only be considered briefly. As can be seen, a digit tone appear at output a5 will be the input to a ban~ of ten receiver detectors R/Dlo to R/Dlg in channel selection circuit 250, only four of which receiver detectors are shown in FIGURE 12.
Receiver detectors R/Dlo to R/Dlg are tuned to receive and detect the tones 4000 HZ to 5800 HZ (digits 0 to 9), respectively. When a digit tone is detected, the output of the receiver detector that detected the tone switches to logical 1. As can be seen, theoutput of each receiver detector is the set input of a corresponding ~30 flip-flop F~lo to F~lg, as the case may be. Likewise, the output of each receiver detector, through set/reset lines 0 to 9 is I
I' 1(~84183 the input of nine logical OR gates associated with the other nine receiver detectors. For example, the output of receiver detector R/D12 is the input of gates ORlo, ORll, OR13 or OR18 (not shown), and ORlg. Thus, when the output of a receiver detector R/Dlo to R/D19 switches to logical 1, the flip-flop FFlo to FFlg, as the case may be, associated with the receiver detector receives a set command causing its output Plo to Plg, as the case may be, to switch to logical 1 (or do nothing if such output is already logical 1). The logical 1 output of the receiver detector that switched also appears, through the OR gates associated with the nine other receiver detectors, at the reset inputs of the other flip-flops associated with the nine other receiver detectors. Accordingly, all such other flip-flops receive a reset command. The output of any such flip-flop that is not already logical 0 is caused to switch to logical 0.
The outputs P1o to Plg of fIip-flops FFlo to ~Flg control switches SW10 to SWlg, respectively, in front wall receiver 531, which, as now considered, is an all-wave 20 receiver, the tuning range of which is changed by switching tuned circuits of the receiver. Switches SW10 to SWlg are normally open but close in response to a logical 1 command ~ from the output Plo to Plg, as the case may be. Ordinarily, -~ only one such switch is closed depending on which output Plo to Plg is logical 1.
The design of all-wave receivers is well known as is the automatic switching of tuned circuits thereof to tune the receivers to receive a desired channel. Accordingly, the -~
detailed circuit design of such receivers will not be considered.
1~84183 Referring again to FIGURE 9, it is apparent that line equipment Ei cannot "know" the channel number of an input from line ~j unless it is told by the calling party. Thus back wall receiver 536 cannot be tuned in response to control signals initiated from line equipment Ej. Any automatic tuning means for receiver 536 must ultimately be controlled by the calling party.
FIGURE 13 (a) and 13 (b) illustrate how line equipment may be modified to allow a calling party to tune the back wall receiver 536 of a called party. As can be seen, FIGURE 13 (a) repeats some of the elementsof FIGURE 9 and includes in addition a 3 MH~ modulator MOD3 and a further hybrid H7a which receives inputs from the output of hybrid H7 on line 515 and from the output of modulator MOD3 on line 515a. The output of hybrid H7a is on line 515a to hybrid H8. Modulator MODl receives as a modulating input on line 515c a HOME TONE which identifies line equipment Ej and consequently the subscriber terminal Tj associated therewith. The HOME TONE, which may be produced by a simple oscillator (not shown) included in line equipment Ej, has a frequency corresponding to the last digit of the number identi-fying subscriber terminal Tj (No. 4828) - in the present case 5600 H~ representing the digit 8. Thus, when PARTY A is the calling party, the output to line Ij includes a 3 MH~ carrier modulated by a 5600 H~ HOME TONE.
For purposes of responding to a HOME TONE received on line ~j , line equipment Ej now includes a home tone receiver 535a as shown in FIGURE 13 (b) plus a modified version of FIGURE
12. Home tone receiver 535a is tuned to receive 3 MHZ modulated carrier inputs from line 535 and produce at its output "to input X" the modulating frequency or home tone. Input X is the 1~34183 ::
input "X" shown in FIGURE 12 wherein (a) front wall receiver 531 is now to be considered as back wall receiver 536; (b) the designation "FROM aS" (FIGURE 10) is to be ignored; (c) the designation~"530" is now to be taken as "534"; and (d) the designation "532" is now to be taken as "537". Also, tuned circuits 10 to 19 in FIGURE 12 are now tuned for LOW channels rather than HIGH channels as shown.
From the description of the tuning of front wall receiver 531, it will readily be concluded that back wall receiver 536 will be tuned for a particular low channel depending on the frequency of the HOME TONE from a calling party.
In some embodiments of line equipment, it may be ~, desirable to tune line transmitters to transmit on a particular channel. For example, according to the fourth method of channel assignment shown in FIGURE 8(a), it is apparent that the line equipment Ek of PARTY B (the called party) must convert channel 4 LOW inputs received on line Lk to channel 8 HIGH outputs to ;
' line ~k~ Since channel 8 HIGH is a channel determined by PARTY A, then line equipment Ek must be conditioned to transmit on such channel by control from PARTY A. Although line equipment Ej shown in FIGURE 9 was not designed for the fourth method of ~-channel assignment shown in FIGURE 8(a), it may readily be concluded that with some modification and the use of HOME TONES
to tune back wall transmitter 510 as well as back wall receiver 536, then, the desired channel assignment will be achieved. Front wall receiver 531 may now be permanently tuned to receive only channel 8 HIGH since this will always be the channel input on line Ij. However, in the called mode of operation the channel received by back wall receiver 536 (a LOW channel) and the channel transmitted by back wall transmitter 510 (a HIGH channell will vary depending on the last digit of the number identifying the calling party. Back wall receiver 536 may be tuned by a HOME
1~84~83 TONE in the manner aforesaid. Similarly, the same HOME TONE
may be used to discretely control the transmitting carrier frequency of back wall transmitter 510 by switching tuned circuits of the transmitter carrier frequency oscillator. -Similar to the case of receivers, the design of transmitters to automatically transmit on one of a number of transmitting frequencies is well known and detailed circuit design will not be considered.
The hybrids shown in FIGURES 9 and 13(a) may be conventional resistive hybrids as shown in FIGURE 14 comprising resistors Rx, Ry and balancing lmpedance Zb The loss through each will be approximately 6 dB, but such loss may be recovered by the line amplifiers AMPl, AMP2 and AMP3 which also compensate for losses in the transmission paths outside the line equipment Ej.
Line equipment_Ej as shown in FIGURE 9 is not suitable to control transmission gates such as are shown in FIGURES 5(a) and 5(b) which require that coded control signals be received within predetermined time intervals. For the circuit of FIGURE
9, the control signals which originate at first instance from the subscriber terminal Tj (not shown in FIGURE 9) in effect flow through line equipment Ej via calling control circuit 509 from line Lj to line Ij at a rate determined by the rate of activity at the subscriber terminal. To produce the control signals required to operate transmission gates such as are shown in FIGURE 5(a) or 5(b), it is contemplated that the calling control circuit would include a storage means to record the number of the called party, and then produce the necessary control signals to close or open the transmission gates during a rapid playback of digits of the recorded number - the order of the digits in the playback depending on whether the transmission - ~84183 gates were to be closed or opened. For the transmission gate of FIGURE 5(b) used as a vertical transmission gate, the two digit tones represen-ting the identification of the incoming line would be added to the playback sequence following the two digit tones identifying the connecting front horizontal trans-mission track. A playback sequence would be initiated on a call from one party to another when the last digit tone identifying the called party is detected by the calling party's called control circuit. Likewise, a playback sequence would !. be initiated when a DISCONNECT tone is detected by the calling party's called control circuit.
FIGURE 15 is a circuit diagram of a transmission gate ' which uses diodes, rather than a mechanically moving part, such as switch SWl in FIGURE 5, to perform gating operations between transmission tracks. The transmission gate in FIGURE
15 comprises two diodes Dgl and Dg2 which are connected back-to-back on their anode sides. Preferably, the diodes are high frequency PIN diodes. The cathode side of diode Dgl is connected to gate contact line 24 and the cathode side of diode Dg2 is connected to gate contact line 25. The transmission gate also comprises two resistors Rgl and Rg2 connected in series between bias control line 26 and the connection between the anodes of diodes Dgl and Dg2. A capacitor Cg provides a circuit path between such two resistors and the outer conductor of the transmission tracks.
The operation of the transmission gate shown in FIGURE 15 is as follows. When the voltage applied to bias control line 26 is zero with respect to the outer conductor of the transmission tracXs (which may be considered as ground), then diodes Dgl and Dg2 are subs-tantially non-conductive. The ` 11[~84183 transmission of R. F. communication signals between transmission tracks is inhibited and the gate is closed. When a positive voltage is applied to bias control line 26, then diodes D
and Dg2 are forward biased and will be conductive to allow the transmission of R. F. communication signals between transmission tracks - the gate is then open. During such transmission, capacitor Cg aids to suppress the appearance of R. F. signals on bias control line 26. It may be noted that the circuit path for bias voltages applied to bias control line 26 can be completed by load terminations (not shown in FIGURE 15~ on the transmission tracks.
In FIGURE 15, it is assumed that the transmission gate is not controlled by code input signals provided as an input to a transmission track, thus there is no probe shown such as probe 87 in FIGURE 5. It is thus assumed that the bias voltages applied to bias control line 26 are determined by means other than code input signals to a transmission track.
As depicted, the transmission gate shown in FIGURE 15 is not in any sense coded, however, it plainly could be coded if so desired. For example, bias control line 26 could be the output of a binary or a binary-coded-decimal comparator having a plurality of digital (logical 0 or logical 1) input lines. The output voltage of the comparator to bias control line 26 would be the voltage necessary to open the transmission gate if and only if preselec-ted ones o~ the digital input lines were at loyical 1 and the remainder of -the diyital inpu-t lines were at lo~ical 0. Theimplementation of such control will be obvious to those ski]led in the ar-t.
- ~0 -1~84183 The branched path, path routing arrangement (FIGURE 1) described in detail herein is characterized by a decimal based system of organization and is symmetric in structure - that is, there are 100 (10 x 10) vertical platforms, each having 100 (10 x 10) vertical tansmission tracks, and 100 (10 x 10) horizontal platforms, each having 100 (10 x 10) cross horizontal transmission tracks.
` For each possible pair of platforms consisting of a vertical plat-form and a horizontal platform, there are 100 (10 x 10) inter-connecting front horizontal transmission tracks. Also, the arrangement was described in terms of being used in a bi-directional communication system wherein 20 (10 x 2) communication channels were present having carrier frequencies in the range from 100 MHZ
; to 290 MHZ.
It will be readily apparent to those skilled in the art ' that a branched path, path routing arrangement in accordance with the present invention could be characterized by some other system of organization, for example, a binary based system of organization -e.g. 64 vertical platforms, each having 64 vertical transmission tracks; 64 horizontal platforms, each having 64 cross horizontal - 20 transmission tracks; and, for each possible pair of such platforms, 64 interconnecting front horizontal transmission tracks. Sixteen channels using part of the frequency spectrum between 20 MHZ and 220 ~Z could, for example, be adopted for use in conjunction with ;
such a system.
Also, as was discussed in the introductory portion of this specification, branched path, path routing arrangements which are not symmetric in their structure are contemplated.
Obviously, many modifications and variations in the present invention are possible in light of the foregoing teachings.
It is, therefore, to be understood that within the scope of the - appended claims, the invention may be practiced otherwise than as specifically described.
- 8~ -
Claims (17)
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. A path routing arrangement for use in a frequency division branched path carrier communications system, said path routing arrangement comprising:
a. an integer number N of first transmission tracks and an equal number of second transmission tracks;
b. branched path means interconnecting said first transmission tracks and said second transmission tracks in a branched path manner for selectively providing a desired carrier transmission path be-tween a preselected one of said first transmission tracks and a preselected one of said second trans-mission tracks whereby a desired transmission path through said path routing arrangement is defined for a first communications carrier having a pre-determined first carrier frequency and propagating in a first direction along the defined path and for a second communications carrier having a predeter-mined second carrier frequency and propagating in the opposite direction along the defined path; said second carrier frequency being different than said first carrier frequency by a predetermined amount;
said branched path means including an integer number N of third transmission tracks defining branching paths between said first transmission tracks and said second transmission tracks; said desired trans-mission path being a transmission path defined by said preselected transmission tracks and a unique one of said third transmission tracks which is inter-- Page 1 of Claims -connected with said preselected first and second tracks; each of said transmission tracks and any carrier transmission path so defined being electri-cally unbalanced and shielded to substantially con-fine communications carriers propagating therein and allowing communication carriers gaining access thereto to propagate in and energize the transmission track or path, as the case may be.
a. an integer number N of first transmission tracks and an equal number of second transmission tracks;
b. branched path means interconnecting said first transmission tracks and said second transmission tracks in a branched path manner for selectively providing a desired carrier transmission path be-tween a preselected one of said first transmission tracks and a preselected one of said second trans-mission tracks whereby a desired transmission path through said path routing arrangement is defined for a first communications carrier having a pre-determined first carrier frequency and propagating in a first direction along the defined path and for a second communications carrier having a predeter-mined second carrier frequency and propagating in the opposite direction along the defined path; said second carrier frequency being different than said first carrier frequency by a predetermined amount;
said branched path means including an integer number N of third transmission tracks defining branching paths between said first transmission tracks and said second transmission tracks; said desired trans-mission path being a transmission path defined by said preselected transmission tracks and a unique one of said third transmission tracks which is inter-- Page 1 of Claims -connected with said preselected first and second tracks; each of said transmission tracks and any carrier transmission path so defined being electri-cally unbalanced and shielded to substantially con-fine communications carriers propagating therein and allowing communication carriers gaining access thereto to propagate in and energize the transmission track or path, as the case may be.
2. A path routing arrangement as defined in claim 1 wherein said first transmission tracks are arranged in n first groups of n first transmission tracks per first group, and wherein said second transmission tracks are arranged in n second groups of n second transmission tracks per second group;
and wherein n is an integer number greater than 1.
and wherein n is an integer number greater than 1.
3. A path routing arrangement as defined in claim 2 wherein, for each particular first group, said branched path interconnecting means comprises a third group of n of said third transmission tracks, each of which third transmission tracks interconnects with each first transmission track of such particular first group and interconnects with each second transmission track of a unique one of said second groups.
4. A path routing arrangement as defined in claim 3 wherein each third transmission track is so interconnected with each first transmission track by a first means for selectively providing a communication path therebetween, and is so interconnected with each second transmission track by a second means for selectively providing a communications path therebetween.
5. A path routing arrangement as defined in claim 4 wherein said transmission tracks are co-axial lines and wherein said first means and said second means each comprise a co-axial switch.
6. A path routing arrangement as defined in claim 4 wherein each of said first means and each of said second means is a coded transmission gate normally closed to prevent carrier transmission between the transmission tracks inter-connected by such transmission gate; each particular trans-mission gate including means for receiving a coded input signal, and, if such coded input signal represents, in a selected code, the identification of such particular gate, for causing such particular gate to open to allow carrier transmission between the transmission tracks interconnected by such particular transmission gate.
7. A path routing arrangement as defined in claim 6 wherein said receiving means of a transmission gate inter-connecting a given first transmission track and a given third transmission track includes means to detect said coded signal input provided as an input to the given first trans-mission track.
8. A path routing arrangement as defined in claim 6 wherein said receiving means of a transmission gate inter-connecting a given second transmission track and a given third transmission track includes means to detect said coded signal input provided as an input to the given third trans-mission track from a first transmission track interconnected to said given third transmission track.
- Page 3 of Claims -
- Page 3 of Claims -
9. A path routing arrangement as defined in claim 8 wherein said transmission tracks are co-axial lines.
10. A frequency division branched path path routing system for interconnecting a plurality of subscriber terminals to allow bi-directional carrier communications to take place between calling ones and called ones of the subscriber terminals, each subscriber terminal being adapted to transmit communications signals on a pre-assigned first carrier frequency and being adapted to receive communications signals on a second pre-assigned carrier frequency different in frequency from the first carrier frequency by a pre-assigned amount; said system including a branched path path routing arrangement for performing path routing operations between called ones and calling ones of the subscriber terminals;
said arrangement comprising:
a. a plurality of each of first and second transmission tracks, each first transmission track and each sec-ond transmission track acting in association with one of the subscriber terminals;
b. branched path means interconnecting said first transmission tracks and said second transmission tracks in a branched path manner for selectively providing a desired carrier transmission path be-tween a preselected one of said first transmission tracks and a preselected one of said second trans-mission tracks to define a transmission path through said path routing arrangement for communi-cations between the calling subscriber terminal associated with said preselected first transmission track and the called subscriber terminal associated with said second transmission track; said branched path means including a plurality of third transmission tracks.
said arrangement comprising:
a. a plurality of each of first and second transmission tracks, each first transmission track and each sec-ond transmission track acting in association with one of the subscriber terminals;
b. branched path means interconnecting said first transmission tracks and said second transmission tracks in a branched path manner for selectively providing a desired carrier transmission path be-tween a preselected one of said first transmission tracks and a preselected one of said second trans-mission tracks to define a transmission path through said path routing arrangement for communi-cations between the calling subscriber terminal associated with said preselected first transmission track and the called subscriber terminal associated with said second transmission track; said branched path means including a plurality of third transmission tracks.
11. A frequency division branched path path routing system as defined in claim 10, wherein each of said trans-mission tracks and any transmission path so defined is electrically unbalanced and shielded to substantially confine communications carriers propagating therein, and to allow communications carriers gaining access thereto to propagate in and energize the transmission track or path, as the case may be.
12. A frequency division branched path path routing system as defined in claim 11 wherein said first transmission tracks are arranged in n first groups of n first transmission tracks per first group, and wherein said second transmission tracks are arranged in n second groups of n second transmission tracks per second group; and wherein n is an integer number greater than 1.
13. A frequency division branched path path routing system as defined in claim 12 wherein, for each particular first group, said branched path interconnecting means comprises a third group of n of said third transmission tracks, each of which third transmission tracks interconnects with each first transmission track of such particular first group and interconnects with each second transmission track of a unique one of said second groups.
14. A frequency division branched path path routing system as defined in claim 13 wherein each third transmission - Page 5 of Claims -track is so interconnected with each first transmission track by a first means for selectively providing a communica-tions path therebetween, and is so interconnected with each second transmission track by a second means for selectively providing a communications path therebetween.
15. A frequency division branched path path routing system as defined in claim 14 wherein said transmission tracks are co-axial lines and wherein said first means and said second means each comprise a co-axial switch.
16. A frequency division branched path path routing system as defined in claim 15 wherein each of said first means and each of said second means is a coded transmission gate normally closed to prevent carrier transmission between the transmission tracks interconnected by such transmission gate; each particular transmission gate including means for receiving a coded input signal, and, if such coded input signal represents, in a selected code, the identification of such particular gate, for causing such particular gate to open to allow carrier transmission between the transmission tracks interconnected by such particular transmission gate.
17. A frequency division branched path path routing system as defined in claim 16 wherein said receiving means of a transmission gate interconnecting a given first trans-mission track and a given third transmission track includes means to detect said coded signal input provided as an input to said first transmission track; and wherein said receiving means of a transmission gate interconnecting a given second transmission track and a given third transmission track - Page 6 of Claims -includes means to detect said coded signal input provided as an input to the given third transmission track from a first transmission track interconnected to said given third trans-mission track.
- Page 7 of Claims -
- Page 7 of Claims -
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA261,634A CA1084183A (en) | 1976-09-21 | 1976-09-21 | Branched path, path routing arrangement and systems |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA261,634A CA1084183A (en) | 1976-09-21 | 1976-09-21 | Branched path, path routing arrangement and systems |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1084183A true CA1084183A (en) | 1980-08-19 |
Family
ID=4106900
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA261,634A Expired CA1084183A (en) | 1976-09-21 | 1976-09-21 | Branched path, path routing arrangement and systems |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1084183A (en) |
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5822312A (en) * | 1995-08-30 | 1998-10-13 | Com Dev Limited | Repeaters for multibeam satellites |
| US5825325A (en) * | 1995-12-21 | 1998-10-20 | Com Dev Limited | Intersatellite communications systems |
| US6047162A (en) * | 1997-09-25 | 2000-04-04 | Com Dev Limited | Regional programming in a direct broadcast satellite |
-
1976
- 1976-09-21 CA CA261,634A patent/CA1084183A/en not_active Expired
Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5822312A (en) * | 1995-08-30 | 1998-10-13 | Com Dev Limited | Repeaters for multibeam satellites |
| US5825325A (en) * | 1995-12-21 | 1998-10-20 | Com Dev Limited | Intersatellite communications systems |
| US6047162A (en) * | 1997-09-25 | 2000-04-04 | Com Dev Limited | Regional programming in a direct broadcast satellite |
| US6498922B1 (en) | 1997-09-25 | 2002-12-24 | Com Dev Limited | Regional programming in a direct broadcast satellite |
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