DE2245708A1 - TWO-STAGE TIME MULTIPLEX TELEPHONE SWITCHING SYSTEM WITH FOUR-WIRE SPEECH-WAY INTERFACING FOR CONNECTION TO A PCM NETWORK - Google Patents

Description

Two-stage time division telephone switching system with four-wire Speech path through-connection for connection to a PCM network The invention relates to a two-stage time division multiplexed voice switching system with four-wire voice path switching for connection to a PCM network, in the first switching stage of the switching system the connections are divided into subscriber groups, special line groups and special groups and the outgoing and incoming connection lines each of a group on separate busbars that can be connected within a group via coupling points are led.

The method of pulse code modulation is used in transmission technology (PCM) are being used to an ever greater extent. In this process, the the pulse amplitude modulation (PAM) resulting samples are digitally encoded and transfer. The advantage of this method is its high level of immunity to interference with simultaneous insensitivity to attenuation fluctuations. The pulse code modulation plays an important role not only in transmission technology, but has also been included in the Ver.

Medium technology input found. However, this is where their advantages lie not so obvious because within a switching system the question of Interference shear is not as problematic as it is with long transmission lines. Various proposals have therefore been made, such as time division switching systems, e.g. PAM or PCM systems, can be interwoven with PCM transmission systems (see NTZ 1968, pages 393-400). A particular nuance of the interweaving between Switching and transmission systems arises when it is a multi-level Time division switching system acts.

In this case, for example, space and time levels can be connected to one another and / or changes to the multiplex format are made (NTZ 1970, pp 465-471).

It is already a two stage time division telephone switching system with four-wire speech through-connection has been proposed, in which the connections are divided into groups, each with its own group connection memory and in which the outgoing and incoming connection lines each have a group on separate busbars that can be connected via coupling points within a group are performed and in which the busbars connected to the outgoing connecting lines of all groups via controllable crosspoints all of them with; the incoming connection lines connected busbars can be connected (see patent application P 2211490.7). In this switching system, the line groups are according to their function in subscriber groups, Special management groups and special groups, each of these groups having one associated group connection memory and for each incoming or outgoing Busbar of a group a busbar connection storage is provided, of the various outgoing or incoming busbars of the individual groups connects to the incoming or outgoing busbars via crosspoints and in which both the group connection stores and the busbar connection stores A central control computer or via a specially trained sewer system can be controlled by a corresponding program control with central memory.

With this switching system, however, it is not possible to get one Exchange information with PCM networks.

lill one a PAM time division multiplex switching system to a PCM network connect, the first question to be clarified is how the analog / digital conversion should be made. A digitization already at the individual participant appears because of the large number of participants and the associated high costs not functional. Another possibility would be the on-the-fly connection of analog / digital converters to those participants who are currently active Der Erfndimg is based on the task in a multi-stage two-way multiplex telephone switching system, which contains at least one PAM stage, a connection for a PCM transmission link to be provided.

This object is achieved according to the invention in that the outgoing and incoming connection lines of those groups of the first coupling stage which are acted upon with low-frequency information signals - for example groups of participants - connected to the second coupling stage via PCM / PAM converter and PCM / PAM converter are, while those groups to which only PCM signals are offered - e.g.

Special line groups that are connected to a PCM network only as transit stations serve, which the incoming PCM signals to the conditions of the two-stage telephone switching system adjust.

The advantages achieved with the invention are in particular: that the PAM /: PCM system has a simple B-coupling stage, with between these B-coupling stage and the periphery a digital information transfer takes place.

An Ausfürrungsbeispiel the invention is shown in the drawing and is described in more detail below! bem. Show it figure 1, the Principle of a two-stage. Time division multiplex switching device for the PCM connection.

Figure 2 shows an excerpt from a subscriber group, dei with the B-coupling stage the two-stage time division switch is connected.

FIG. 3 shows an adaptation circuit for private branch exchanges whose PCM bit frequency differs from the bit frequency of a PCM network.

FIG. 4 shows a section from the B coupling stage.

FIG. 5 shows a pulse diagram for FIG. 2.

In the figure 1 is a two-stage time division multiplex switching device shown with the coupling stages A-KS and B-KS. The A-coupling stage A-ks consists of several groups. e.g. from the participant groups TNG, the special management groups SLG and the special groups SNG. Of these groups, FIG. 1 only shows each represented a group. The group of participants TNG, which in practice accordingly the expansion of the switching system occurs many times, is used to connect the subscriber intercoms TSS via the subscriber circuits TS to the coupling stage A-KS. While the individual Speech paths are brought up to the A-coupling stage A-KS, the connection states are (e.g. "free". "occupied") from a scanner AT1 via the channel head KK-AT1, the status and command channel ZBK and reported to the control computer SR via the channel control KSt, which the corresponding control commands via the status and command channel ZBK to the There are coupling stages A-KS and B-KS. Both coupling stages actuator based on the received Commands the desired new connection states.

In a corresponding manner, the continuing lines, e.g. 3. Cross-connection or extension lines via Cross-connection transmissions Q-Ue or extension line transmissions NAL-Ue connected to the coupling stage A-KS. According to the mostly higher traffic on this one Lcitungem is the Anschlusszjiil in the special management groups SLG mostly lower than in the TNG participant groups.

The special groups SNG are used to connect operator stations BP and switching broadcasting equipment. such as conference facilities, Data stations DS and video telephones via appropriate circuits DSS, BPS, to the A coupling step and A-KS. Apart from special features for broadband transmission In the special groups SNG, all details of the A coupling stage A-KS are identical built up. Jcder group is assigned a part of the A-coupling stage A-KS, which has a corresponding channel head KK1, KK2, KK3 to the data and command channel ZBK connected.

In contrast to a two-stage time division multiplex switching device, This switching facility is built on a pure PAM basis special coupling elements between the A coupling stage A-KS and the B coupling stage B-KS on.

These coupling elements are converters W1, W2, W3. These converters are for the TNG subscriber group and the SLG special line group of such a nature that they convert PAM signals to PCM signals and PCM signals to PAM signals can convert. For the special group SNG it is assumed in this example that that it is already acted upon by PCM signals that are only sent to the switch-internal PCM pulse frequency must be adapted. As a result, there is no need for the special group SNG a scanner and a PAM / PCM -or. PCM-PAM converter as converter W3. Of course the converter W2 of the special line group SLG can also be used in the same way as the converter W3 of the special group SNG, albeit the special management group SLG is already being supplied with PCM signals. The group of participants TNG should meanwhile always be set up as a pure PAM subscriber group.

In Fig. 2 a part of the participant group TNG is shown again, which is connected to the B coupling stage B-KS. The subscriber circuit TS of a subscriber station is via the amplitude sampling transmitter APS on an A-busbar A-SS1 and via an amplitude sample receiver APE connected to an A-busbar A-SS2. The two A busbars A-SS1, A-SS2 can be connected to isolating amplifiers V1, V2 and can be connected to one another via a group switch GS. The one from the subscriber circuit TS coming amplitude samples can, for example, be a cross-link transmission Q-Ue are supplied via the B coupling stage B-KS.

They arrive via the amplitude sampling transmitter APs, the isolating amplifier V1, the connecting group switch VG31, the matching circuit (sample and hold amplifier) ANP1 to the actual analog-to-digital converter ADW, which in turn is connected to a parallel-to-serial converter PSW is connected, which is connected to the B coupling stage B-KS.

In a similar way, a PCM word that comes about from an office broadcast is given to the B-coupling stage B-KS, via the series-parallel-Wand3er SPW, the Digital-to-analog converter DAW, the adaptation circuit ANP2, the B-busbar B-SS2, the connection group switch VGS2, the isolation amplifier V2 and the amplitude sample receiver APE get to the subscriber circuit TS. The amplitude sampler is activated, the amplitude sample receiver, the group switch GS and the connecting group switch VGS1, VGS2 through a group connection memory VSP-G, which is expediently as Circulating memory is formed and a memory controller S.P-St and a Channel head KK is on the data and defective channel ZBK.

In Fig. 3, a matching circuit is shown which is used to the to convert signals coming from a public PCM network into a frequency that the private branch exchange shown in Fig. 1 is closely matched. The PCM system 30/32 according to CEPT and the CCITT recommendation G717 can be assumed. The following features are relevant here: 1. The sampling frequency is 8 kHz 2. The Analog-digital conversion takes place using 212 = 4096 steps.

3. The 12-bit signal is companded to 8 bits.

4. The companding is carried out using the A curve.

5. Each channel consists of 8 bits.

6. A frame consists of 32 channels (256 bits). It is divided in 30 telephone channels, 1 synchronization and 1 general purpose channel.

7 A crosstalk attenuation of 65 dB is achieved.

As can be seen from this, such a PCM network offers per cycle 32 words of 8 bits each are accepted as information. Assuming now that the one shown in FIG Switching system processed 64 time slots per scan cycle, some result Adjustment difficulties. These adaptation difficulties are thereby (codecs) overcome the fact that 2 PCM terminals work alternately. *) The first device will be assigned to the odd time slots and the second terminal to the even time slots.

The fact that the 64 PCM channels from the PCM network are only 60 voice channels and have 4 data channels is irrelevant, because the 4 data channels can, for example separated by means of the PCM interface of the Coaecs 1,2 and given to the scanner AT will. The scanner now only needs to have the characteristics of the PCM line in one of the Convert stener calculator SR according to the form.

The 60 voice channels of the public PCM network have a structure of 8 bits per channel. Because of the higher crosstalk attenuation required in extension lines a 14-bit conversion and companding is used in the extension line according to FIG. 1 to 10 bits The 8-bit word of the public PCM network must be connected to the 10 Bit word of the private branch exchange can be adapted. This is relatively easy to do, since in principle the same compading characteristic is used for companding of the 14-bit word becomes the *) Such terminals are already known (cf.

Brochure "Pulse Code Modulation Device PCM 30" AEG-Telefunken N2 / WB 845 brief description 03.70) Number of 8 segments per quadrant, adhered to and only the number of quantization levels in the y-direction around the Factor 22 = 4 (2-bit extension) now increased to 26 = 64 levels. The real one Adaptation of the PCM words of the public network to the internal frequency of the private branch exchange takes place in the format converters FW1, FW2. Here, when traffic is coming, the last of the 8 bits 2 bits with the content 00 appended and for outgoing traffic the the last two 'bits of the 10-bit word are deleted. Before transport to the B coupling stage B-KS are the alternating incoming from the two codecs 1, 2 and in the format converters FW1, FW2 words brought to 10 bits in stack memory StSp stacked line-by-line, i.e. nested and thus synchronized with the frequency of the private branch exchange. In the case of 60 PCM channels described here, since the in the concept of Private branch exchange according to Fig. 1 provided connection groups memory VSP-G (Fig. 3) Has 64 lines, 4 lines unused for speech communication.- These lines can can be used for chronization.

As already mentioned, the circuit arrangement according to FIG applied when using a time division multiple access telephone system with a PCM network different clock frequency is to be connected. To this end, two Channels PCM / 32 K, PCM / 32 K of the public network selected and on separate codecs 1, 2 given. The bits of codecs 1, -2 are then transmitted via format converters FW1, FW2 shifted in time and in one. Stapiispeicher StSp nested in one another in a timely manner. In the structural implementation, the format converters FW1, FW2 can be in the stack memory The bits qf pass from the Stapelapeicher StSp to a parallel-to-serial converter PSW1, in turn via the connection group switch VGS3, VGS4 with the B-coupling stage B-KS connected is.

In the figure 4 is an embodiment of a B-coupling stage B'KS shown. This switching stage is constructed in such a way that the sending B-voice busbars one group with the receiving voice buses of all other groups each one B-coupling point BKP can be connected.

For example, becomes a subscriber station in the subscriber group TNG, which works on PAM basis, called over a public PCM network, so play the following processes via the B coupling stage B-E3 from the PCM words from the public Network arrive at an office transmission of the private branch exchange eem, Fig.1, which is practical only has an adaptation function and has a circuit arrangement according to FIG shows. In this office transmission, the PCM words coming from the network are received the time conditions of the extension position, adapted and via the connection group switch VGS 3, VGS 4 on the busbars B-SSn or B-SSnl. Get from there via coupling points BKP to busbars B-SS1, B-SS2 and from there to already described way to the subscriber circuit TS. The crosspoints are BKP Opened via the connection memory VSP-SS for as long as a complete PCM word can be transmitted.

With the aid of FIG. 5, it will now be explained once again which course takes a pulse amplitude sample within the circuit arrangement according to FIG. after this an amplitude sample from the amplitude sample transmitter β from an analog speech signal is picked out, it is amplified by the amplifier V1 and arrives - Since it should not be an internal call via GS - via the connection group switch VGS1 on the saddle rail B-SS1 (a). From the busbar B-SS1 becomes the Amplitude sample via matching circuit ANP1 to the analog-digital converter ADW given where it is digitized (b). After digitization takes place in the parallel to serial converter PSW a series implementation takes place (c). The bits that are now available in series are B-coupling stage B-KS supplied, where it is fed into the series-parallel converter via a coupling point BKT (d) SPW arrive and are converted back into parallel bits there (e). In the digital-to-analog converter DAW converts the parallel digital signals back into an analog signal (f) and via the matching circuit ANP2 and the busbar B-SS2 to a second Participants fed. From Fig. 5 it can be seen that between the individual conversion processes Certain times pass, mainly due to runtimes and conversion times are conditional.

Claims (5)

Patent claims: 1. Two-stage time division telephone exchange system with four-wire Speech path through-connection for connection to a PCM-Metz, whereby in the first coupling stage of the switching system the connections in subscriber groups, special line groups and special groups and the outgoing and incoming connection lines each group on separate, but within a group via crosspoints connectable busbars are guided, characterized in that the outgoing and incoming connection lines of those groups of the first switching stage (A-KS @ to which low-frequency information signals are applied - for example Participant groups. (TNG) - via PAM / PCM converter (W1, W2) and PCM / PAM converter (W1, W2) with the second coupling stage (B-KS) are connected, while those groups, which only PCM signals are offered - e.g. Special line groups (SLG) connected to a PCM network - only serve as transit stations, which the incoming PCM signals so the conditions of the two-stage telephone exchange system. fit. 2. Two-stage time division multiplex telephone switching system according to claim 1, characterized in that in the second coupling stage (P-KS) that of a certain Connection group outgoing busbar via a switch (B-KP) with the incoming Busbar of every other connection group can be connected. 3. Two-stage time division multiplex voice switching system according to claim 1, characterized in that the transmission of the PCM words via a crosspoint (BKP) of the second coupling stage (B-KS) takes place in series. 4. Two-stage time division multiplex telephone switching system according to claim 1 characterized by the fact that the line groups in the first group level (A-KS), to which PCM words are applied which have a word frequency of m / 2, where m is the frequency for which the switches of the second coupling stage are designed are, only have an adaptation function, which is that every two incoming PCM channels of the word frequency m / 2 are interconnected so that they result in a total frequency in. 5. Two-stage time division multiplex telephone exchange system according to Claim 1, characterized in that with a different number of bits per PCM word in the public PCM Metz and in an extension length the format conversion takes place in that the number of quantization levels according to the A characteristic in y-direction is increased by a factor of 2² = 4, so that the application or omission the lowest possible bit in the word. L e r s e i t e