US2459131A - Electronic distributor for multiplex pulse communication systems - Google Patents

Description

Jan. 1l, 1949. M. H. MEsNER .2,4593

- ELECTRONIC DISTRIBUTOR FOR MULTIPLEX PULSE COMMUNICATION SYSTEMS Filed Sept. 24, 1946 6 Sheets-Sheet l ma Zf'TA-vf /WL rrr ATTORNEY Jan. l, 1949. l M. H. MEsNER ELECTRONIC DISTRIBUTOR FOR MULTIPLEX Y PULSE COMMUNICATION SYSTEMS Filed sept. 24, 194e 70 MM mi?" INVENTOR M4): 1% MJA/M. BY )f Q A'I-T R NY C /61 l QV 4MM/qm -l Y loFgl M. H. MESNER ELECTRONIC DISTRIBUTOR FOR MULTIPLEX PULSE COMMUNICATION SYSTEMS Jam., f, E949.

6 Sheets-Sheet 3 Filed sept. 24, 194e Jan. 11, 1949. M. H. MESNER 45mm ELECTRONIC DISTRIBUTOR FOR MULTIPLEX PULSE COMMUNICATION SYSTEMSl Filed sept. 24, 1945s e sheets-sheet 4 f ATm/M/EY Jan. 1l, i949. M. H. MEsNER 2,459,131

ELECTRONIC DISTRIBUTOR FOR MULTIPLEX PULSE COMMUNICATION SYSTEMS Filed Sept. 24, 1946 6 Sheets-Sheet 5 dm El@ ...um nimh w I H w+ m um m .M M n 114 111111:(1 11`r1d m M m Nw rlm m .f7 n QN .J Q., @uw @m www m k O IT mm M m @NWA um ww \N Nx b1 1 A WN Lr a P W rl Fl W .MTHU um n QCD H n n@ y mm, m .v A A -mWFLV M. H. MEsNER 2,459,131 ELEcTnoNIc DISTRIBUTOR Fon MULTIPLEX PULSE COMMUNICATION SYSTEMS 6 Sheets-Sheet 6 A HU HU =L S1 A Av Uv III www IQQ n" u" www. mm .All 45%. un A INVENTOR. Mm' A. /I/fs/VEP BY j 7 A/EX Jan. V11, 1949.

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A vv Patented Jan. 11, 1949 i UNlTED sm ELECTRONIC DISTRIBUTOR Fon MULTI- PLEX PULSE COMMUNICATION SYSTEMS Max IVI. Mesner, Princeton, N J., asslgnor to Radio `Corporation of America, a corporation of Dclay Ware Application september 24, 194s, serial Ne. 698,931

This invention relates to electronic distributors and more particularlyto a device for use in multiplex communications systems. My invention makes it possible to multiplex any desired kind of signals without appreciable distortion by compressing. each signal train into discrete channel-time units,transmitting the compressed signal components for the different channels in successive order, and expanding the same after reception so as to restore their original frequency characteristics and continuity.

The instant application is a continuationin part of my co-pending application Serial No. 496,921, entitled Multiplex system, and lcd July 31, 1943, now'abandoned.

In multiplex systems, the present trend of design is to do away with all moving parts such as rotary commutators, magnetic selecting relays,

' and the like. It is advantageous to perform the necessary switching functions for impressing signals successively on different channels by means of electronic switches. y One known method is to arrange a series of electron discharge tubes with circuit parameters such that each tube is activated in succession and prepares a succeeding tube for activation. If, therefore, the multiplex system requires transmission of separate trains of signals on three different multiplex channels, then three such discharge tubes in the electronic distributor would be provided and transmission on each channel would t'ake place during the period of activation of each individual tube.

Another known method of electronic switching requires the use of a special cathode ray tube having a plurality of target anodes against which an electronic stream is directed from a gun in the tube. The defiecting means operates cyclically and the electron beam is controlled by means of the signals. It, therefore, follows that different signals may be directed into different channels each associated with one of the target anodes.

My improvements in electronic switching are entirely different'from those described in the foregoing paragraphs.

Cathode ray tube technique is preferably employed in such a manner that by one scanning operation intelligence is stored inthe form of electronic charges spread over a field. The scanning operation herein referred to is intended to mean that electrons emitted by a so-called electron gun" are deflected toward different portions of a field or target. ASuch a target as employed in my invention is composed of an array of mutually insulated linear conductors arranged 17 Claims. (Cl. 179-45) preferably as elements of a cylindrical surface and backed by a conducting plate which is spaced from the conductors by a dielectric of substantially uniform thickness. The intelligence to be transmitted is broken up into different por tions, each portion of which represents a scanning cycle. The storing operation of the transmitter is, however, continuous. During the latter portion of each scanning cycle of a so-called put-on beam, a second scanning operation takes place by means of a second or take-off beam which removes the stored intelligence at an accelerated rate, transferring it to an amplifier.

Accordingly, a method will be explained and y apparatus described in the instant disclosure for performing this method wherein an individual signal is impressed on the control grid of an electron gun constituting one unit in a specially constructed cathode ray tube Where two such guns are provided. Independent deflecting means are associated with each gun. The beams. however, are directedagainst the aforementioned target which serves as an anodal screen and possesses a function similar to that of the wellknown cathode ray tube'screens used in television apparatus of the iconoscope type. The tube is also provided with a second gun having separate deecting means associated therewith, The scanning rate for the two beams is made quite differenti although the repetition rateis the. same. The two beams will be hereinafter referred to as the put-on beam and the take-0E" beam respectively. If the scanning velocity of the "take-off beam is made three times as great as that of the put-on beam, then a threechannel multiplex system is provided. Two thirds of the cycle is used as a rest period for the beam which isdeflected at the greater scanning velocity. As a result, the intelligence taken from the tube is condensed as to time and is transmitted in only a fraction of the distributor cycle.

Other objects of my invention, as well as cer-l tain advantages thereof, will best be appreciated as the details of the disclosure areqbrought out. -=v

The following description is 1 accompanied by drawings, in which:

Figs. 1 and la (when Joined together) show diagrammatically a preferred transmitting circuit arrangement including electronic distributors for,

three separate channels in a multiplex system;

Fig. 2 shows a suitable scanning circuit for the "take-oil?" beam of a cathode ray tube distributor; Fig. 3 shows a corresponding scanning circuit for the put-on beam;

Fig. 4 shows a block diagram of receiving apparatus which is associated with electronic distributors of the type `herein disclosed; and

Figs. 5 and 5a (when joined together) show certain details of a circuit arrangement for association with the cathode ray receiving distributor which I preferably employ. l

At the outset it should be understood that Ido not claim as my invention any of the improvements to be found in thespecial cathode 'raytube having two guns and a screen-like target composed of parallel conductors 'which are' insulated one from another. The detailsI of such a; construction are fully disclosed in a copending application of Harley Iams et al'.,"Seria'l` No, 492;658, filed June ze, 1943.` e i.

The two-gun cathode ray tube` l In order to more understandably follow-the ensuing description of my improved circuit arrangements, the essential details of construction of the aforementioned special cathode ray tube having two lguns will first be set forth.

Although the same tube may be used both for 4 the various tube electrodes are indicated on the drawing merely by way of example. These operating voltages may, if desired, be derived from diierent taps on a potentiometer l which is connected between the'positive and negative terminals of a direct current power supply source. An intermediate point on this potentiometer is grounded. `Ground potential is also applied to the anode 2| 22.

The storage screen Il may be constructed in various ways. .ll Inone of the preferred constructions, as indicated inthe copending Iams et al. application, it comprises a supporting sheet of mica about 0.001 inch thick which has an array of parallel conducting strips or lines 24 extending horizontally across the screen. These strips may be formed, `for example, byI sputtering a conductive coating of platinum upon each side of the mica sheet and then using a ruling machine to scratch vabout 100 lines to the inch on the front lso as to separate the metal into conducting lines. The metal coating on thev back side of the mica sheet may be used as the signal plate foi-taking anche signal; if desired. i

In order to insure the operation of the "put-on and to 'one of the deilecting plates gun so that the ratio of secondary electronsto primary electrons shall be greater than unity, a

small amount oi'l caesium may be inserted in the tube during its manufacture. It is preferred, however, that the screen II shall not be photoelectric in action. Therefore, vno oxidizingstep is required preliminary to theintroduction of the caesium. I i

The screen II when mounted in the tube preferably is curved to'conform to the surface of a cylinder having "an axis thatpasses through or y near the centers of deflection of the two electron beams, whereby the point of smallest beam diameter is always at the screen surface as thebeam is deflected and whereby the beams during deflecv surface where the beam strikes.

tion are substantially at right angles to the screen This feature is g, particularly important in the' .operation of the transmission and for reception, the essential details of the tube structure are best shown in Fig. 5, in association with a receiving circuit. The tube comprises a high evacuated envelope having a bulb portion I0, in which a `storage screen is mounted. This screen is a target anode having L low velocity beam.

. In operation the incoming signal is applied to the control electrode I1 to modulate the intensity of the high velocity beam as it is deflected transversely 'across the conducting strips 24. The number of secondary electrons liberated from the strips exceeds the number of beam electrons, and

parallel-disposed conductors 2l which are insulated one from another.

The put-on gun is mounted in the neck porj tion I2 and-the take-off gun is mounted in the neck portion I3. The put-on 4gun emits one beam of electrons, andthe take-off gun emits a second beam. High electron velocity and low electron velocity beams (as distinguished froml scanning velocities) are sometimes used for the put-on and take-off operations respectively, and in much the same manner as has been found -successful in television technique, as is well et al. Operating voltages that may -be applied to Other deecting plates 25 may bel since substantially all of the secondary electrons are drawn overto the collector electrode, they are not redistributed `over the target I I. Hence,

r the bombarded strips 2l are given a more positive potential. Y

At the other end of the screen II the conducting strips are scanned at a. greater speed-by deecting the low velocity electron beam transversely by means of a deilecting coil IIL If the electrons of this beam strike the Aconducting strips 24 with a relatively low velocity, the ratio of secondary electrons to primary or beam electrons (those of the. beam) is less than unity. Accordingly, suiilcient beam current is provided toreturn the conducting lines tothe potential of the cathode supplying this low velocity electron beam.

4'raus the signal put-on by thenrst beam is suls tantially completelywiped oifby a single scanning of the second beam.

The output signals produced by this wipingoif" action may be derived from a signal plate SP on the backside of the screen I I, or they may be derived from a collector electrode 200, or from an electron multiplier receiving the unused electrons from the "take-oil beam as they return from the screen II. These methods of taking oil. a signal from a storage screen are well known in connection with the operation of Iconoscopes and Orthicons. The electron multiplier arrangement for receiving the unused electrons from the take-oil beam is illustrated and described in connection with Fig. 1 of copending application Serial No. 492,658, now Patent No. 2,454,652, granted November 23, 1948, iiled by Iams et al., to which reference is made.

If either of the above described methods of taking oil the signal is employed, the tube is provided with a mica partition I to prevent secondary electrons emanating from the upper portion of screen I I, produced by the put-on" beam from reaching the electron multiplier or collector electrode located in the lower neck I3 of the tube. Also, a metal ring electrode 202 near the partition may be provided and held at a negative potential to repel any secondary electrons that might otherwise get past the mica partition In the example illustrated, the take-off beam is produced by an electron gun which comprises a cathode 36, a control electrode 31, a screen grid 38, a rst anode 39, and a second anode 4I.` One or more electrodes such as 42 are positioned betweenthe second anode and the screen II for slowing down the electrons after they leave the region of the second anode.

The transmitter A block diagram of a preferred circuit arrangement for the transmitting station is shown in Figs. 1 and 1a. In order to maintain a suitable phase differencebetwen the operation of the different cathode ray tubes I0a, I0b, and I0c respectively, a single oscillation generator I producing sine Waves is provided in combination with a delay network comprising series capacitors 2 to 6 inclusive and shunt resistors R2, R3, R4, R5, and R6 respectively. This network has its components so chosen that a phase dilerence of 60 between the different taps from the network is obtained. The energy from the generator 1 is, therefore, fed directly, and with zero phase, to a limiter and pulse generator circuit I2. With a. 60 delay, it is also fed to a limiter and pulse generator I4. The details of these limiters I2 and I4 will be hereinafter described in more detail. The output from the pulse generator in the unit I2 is used to control a saw-tooth generator I5. This generator delivers an output which has its peaks clipped by the device I8. The output from the unit I8 is then amplified in a device 20 and fed to a deflection coil or coils a associated with the take-off gun in the cathode ray tube I0a. The circuit is completed to ground through a centering potentiometer 3I. The tap on potentiometer 3| is coupled to ground across a capacitor 32a.

The limiter and pulse generator unit I4 operating with a phase lag compared with potentials fed to the limiter I 2 is used to control a sawtooth generator 23 which delivers its output to an amplier 26. The amplied energy is fed to one of the deflecting plates 22 in the put-on gun of the cathode ray tube I0a. The opposing beam deflecting plate 22 is connected to ground. As a matter of fact, the 60 delay relationship in the output from the amplifier 26 compared with that from the amplifier 20 should be considered in a diierent sense; that is to say, the beam deection produced by the electrostatic plates 22 has a 300 lead over that of the deecting action of the coils 30a. In other words. a signal which is put-on by the beam emanating from the cathode I6 precedes the "take-off action produced by the beam emanating from the cathode 36.

The intelligence or signal impressed upon channel A may comprise suitable source of modulation. It is herein shown as originating at a microphone 40. The intelligence may, however, be other types of signals, such as television and facsimile, rather than speech as shown. The signal is-amplied by the unit 43 and applied to the control electrode II through capacitor 44, by producing potential variations across the input circuit resistor 45. This' resistor terminates in a tap 46 on a voltage divider, the diierent sections of which extend across the terminals of a direct current potential source.

As will be understood from the foregoing description of operation of the cathode ray tube, the incoming signal is impressed upon element I1 as a result of which, in conjunction with the scanning, there will be a series of charge patterns continually impressed upon the target screen I la, the linear elements 24 of which are arranged to be scanned by the operation of the beam deecting potentials impressed on the electrostatic plates 22. As has also been explained, the take-oil operation is intermittent because the scanning produced by the deflecting coils 30a operates under control of a clipped saw-tooth wavederived from the amplifier 20. The scanning velocity of the "take-0E beam is three times as great as that produced by the electrostatic plates 22 which affects the put-on beam. The takeoff gun is here considered as operating in zero phase relation to the source I. By selection of suitable Values for the time constant elements 65 and 69 and by the use of the clipper diode unit I8 (note Fig. 2) the actual scanning time of the take-01T beam is reduced to one-third of the scanning time of the put-ori beam. This permits rest periods to take place in the output from the screen IIa suiiicient for the impress on the transmitter modulator of signals pertaining to channels B and C.

The circuit arrangements for channels B and C are identical with channel A and need not, therefore, be described in detail. It should, however, be noted that the different sections of the delay network comprising the shunt capacitors 3 to 6 inclusive and series resistors R3 to R6 inclusive provide the necessary delay action in the scanning potential circuits so that the total transmission time for the multiplex system may be enamplied in a pentode tube 34. The diierentiating action is obtained by means of capacitor 32 and resistor 35 the values ofwhich are suitably chosen for the purpose. The maximum potential drop through resistor 3Ia occurs at the instant of the return stroke of the saw-tooth scanning cycle. The input circuit for tube 34 includes grid resistor 35 which is connected to ground. Capacitor 26 couples the cathode of tube 34 to ground and is in shunt with the cathode resistor R8.

target screens I Ia, IIb and IIc which may result from the scannings of the screens by the puton beams.

The electrostatic signal plates SP which are disposed in the rear of the target screens are respectively coupled to the cathodes of the diodes 48a. 48h and 48e by means of capacitors 1a, 1b and 1c. Each said cathode is connected to ground through a resistor 59. A threshold bias is chosen for these diodes such that the noise effects will not be rectified. but only the signal'potentials which exceed the valuey of the steady threshold bias. This bias is obtained by the use of potentiometers 8 connected between the +B supply terminal and ground. The adjustable tap on each of these potentiometers is connected through a resistor 9 to the anode ina respective one of the diodes 48a, 48h and 48e. A

The amplitude of the signal potentials resulting from the scanning action of the take-off beam greatly exceeds what it would be if the scanning velocity were to be the same as that of the puton beam. Allowing for losses, the ratio of the take-off amplitude to the "put-on amplitude approaches 3 to 1. Hence it is quite practical to clear the diode output circuits of adverse effects from the uninterrupted action of the put-on beam in each of the cathode ray tubes I ila, IIib and |00.

The output from each of the diodes 48a, 48h and 48e is coupled through capacitors 29 to the irst grid 28 in an amplifier tube 21, this tube being preferably a pentode. Tube 21 amplies the signal potentials which are successively derived from the three diodes 48a, 48h and 48e. A similar pentode tube 34 ampliiies the synchronizing signal as previously described. The output circuits of the two pentodes are joined together. They have a common load resistor 61 and a common coupling capacitor 41 through which the signals are impressed upon a modulator (not shown) in the radio transmitter,

The input circuit for tube 21 includes components 35, 26 and R8, the same as for tube 84, although their values need not necessarily be the same. The control grid 28 is driven negative by the rectied signals from the three diodes. With due regard for phase reversals additional stages of amplification may optionally be provided.

The circuit arrangement for devices I2, I5, I8 and 20 (Fig. 1) is shown in detail in Fig. 2. From the generator I potentials are fed across capacitor 50 and load resistor 5I to ground. They are also fed through resistor 52 to the control grid in a pentode tube I2, which is used as a limiter device. The circuit arrangement for tube I2 is conventional, comprising, as it does, an output circuit resistor 54, a screen grid resistor 55, a cathode resistor 56 and bypass capacitors 51 and 58. Capacitor 511s connected between the screen grid and ground, while capacitor 58 is in shunt with resistor 56.

The limiter tube I2 produces a substantially square wave output. This output is coupled across capacitor 59 which with resistor 68 acts as a diierentiatorv circuit producing discrete pulses which are fed across capacitor 6| and which are suitable for controllingv a saw tooth generator comprising discharge tube I5. Grid current owing in resistor 62 develops bias for A'insured by the use of a capacitor 650i proper value coupled across the cathode and anode of tube 58. The value chosen for resistor 88 is also important.

A diode rectifier tube I8 is used 'to clip-the peaks oi! the saw-toothwave. The cathode in tube I8 is connected to a' suitable `tap 61 on a' vvoltage vdivider 68, the latter being connected between the ground and a source oi positive D. C. potential indicated by a +B terminal. Resistor 69 is in the anode circuit of tubes I5 and I8.

The action of tube I8 is to dissipate all of the energy peaks above and established potential gradient. The energy impressed across capacitor 18 and load resistor 1I is, therefore, of limited duration and is such as to impress the clipped saw-tooth wave potentials on the amplifier tube 20 for only one-third of the total time.

Tube 20 is preferably of the beam power ampliiier type. Its construction is well known in the art and need not be described herein. This tube, however, is provided with a cathode resistor 13 shunted by capacitor 14. The screen grid resistor 15 has a suitablevalue for producing the necessary screen grid potential. The screen grid bypass capacitor 16 dissipates alternating potentials on this electrode by diverting them to ground. The output circuit for tube 20 includes the deecting coils 30 in shunt with a choke 11. A bypass condenser 49 completes the A. C. path to ground.

In the operation of the circuit arrangement of Fig. 2 a suitably clipped saw-tooth wave is fed to the deflecting coils 30 and the resultant scanning operation of the take-oi beam is produced. In this scanning operation, however, it is necessary to provide a centering adjustment and this is obtained by suitable setting of a tap 18 along a potentiometer 19, the latter being connected between the +B terminal and ground.

Referring now to Fig. 3 a circuit arrangement is shown which indicates the details of devices I4, 23, and 26 as shown in Fig. 1. The circuit components for the limiter and pulse generator tube I4 are exactly similar to those pertaining to tube I2 in Fig. 2. The function of tube I4 is also the same, that is, it provides a limiting action with respect to the sine wave output from the generator I. The resistive elements and 82, together with the capacitative elementsll and 83, constitute a diierentiator which alters the shape of the rectangular wave ouput from tube I4 for suitable control of the grid 84 in a discharge Atube 23. This tube delivers a saw-tooth wave across the load resistor 85. The values of resistor and of the associated capacitor 12 are suitably chosen for producing the desired slope of the saw-tooth Wave. Utilization of the output is obtained by coupling across capacitor 86 to a grid resistor 81 in the input circuit of amplier tube 26. The saw-tooth wave is here amplified in the usual manner, and since the gir.,- cuit arrangements for this tube are conventional they needv not be described in detail. The sawtooth wave potentials are produced across the load resistor 88 and provide beam deecting potentials across the deilecting plates 22 by coupling the s'ame through capacitor 89. The pair of deilecting plates 22 will be understood to control the put-on beam in any one of the three tubes Illa, Illb, and ic.

The receiver It might be well to state briefly the functions which are to be performed by the receiving apparatus in order to separate the received signal into its channel components. As shown in Figs. 4, 5, and a, the signal, after suitable amplification by conventional radio receiving apparatus. is directed into different channels, one for the synchronizing component and the other for the intelligence portion of the signal. Figs. 5 and 5a show details of the circuit arrangement. Considering the signal component which constitutes the intelligence for channel A, this is applied to the put-on" beam of the cathode ray tube l0. However, only one-third of the total time represents the signal applicable to channel A and for the remainder of the distributor cycle a cutoi bias is required so that inappropriate portions of the intelligence signal shall have no eiiect.

The deflection plates of the tube for channel A, for example, cause the put-on beam to have an accelerated scanning velocity such as to completely scan the target from side to side during one-third of the distributor cycle. There are a suilicient number of elemental conductive strips 24 so that the characteristics of the signal remain unaltered but can be reduced to their original frequency by the slower scanning velocity of the take-off" beam. It will thus be'seen that the accelerated modulation frequencies of transmission which are necessitated in order to apply three different trains of signals to the multiplex channel are finally restored in the receiving ap paratus to the normal frequencies of the original modulation sources.V Each channel considered by itself then delivers a continuous ow of modulations to its responsive device.

Referring now to Fig. 4, conductor 90 is connected to the output side of any suitable receiver. Conductor 90a leads to apparatus which is receptive of the intelligence portion of the signal while conductor 90b feeds to a detector for the synchronizing pulses of the signals. This detector is labelled 9|. Its output is fed to an inverter and saw-tooth channel 92 and thence to a device 93 for clipping the peaks of the saw-tooth Waves so as to render only one-third of the wave cycle effective for beam defiection in the tube of channel A. The output from the clipper device 93 is, therefore, fed to an amplifier 94 and the output of the latter is utilized for beam deflection as disclosed in more detail in Fig.- 5.

A component of output energy from the clipper 93 is also directed into a blanking device 95 which is used for producing a cut-od condition in the put-on" gun of channel A during two-thirds of each scanning cycle. The technique for accomplishing this will be explained hereinafter.

A 60 delay in the cyclic operation of the defiecting coils associated with the ftake-of beam is produced by the multivibrator circuit 96. This circuit derives its control from the detector unit 9|. The output from the multivibrator 96 is fed to a. phase inverter and saw-toothgenerator 91 and thence to an amplifier 98 for producing suitable beam deflecting energy to be applied to the deecting coils 3l) associated with the take-off beam.

Another energy component derived from the multivibrator 96 is directed into a circuit arrangement for channel B which is in all respects similar to that which has lust now been described pertaining to channel A. Thus, the output from the multivibrator device 99h has a 120 phase lag relative to the output pulses from the detector unit 9|. The interconnections between the different units 9|, 98, 99h, 96h, 99e and 96e are made such that a 60 phase delay takes place in each step. The channel time is, therefore, divided between channels A, B, and C so as to suitably distribute intelligence signals into their respective responsive devices,

In view of the similarity between'the circuit arrangements appropriate to the different channels, it is not necessary to further describe Fig 4. Reference will, therefore, be made to Figs. 5 and 5a for the circuit detalls which may be considered in connection with any one of the multiplex channels.

In the upper portion of Fig. 5 I show four electronic tubes which represent portions of the scanning circuit arrangement for the put-on beams.

The diode detector |00 has its cathode coupled through capacitor 0| to the conductor 90 from which the signals are derived from the receiver. A threshold action is produced in the diode by virtue of the connection of its anode through resistor |02 and a tap on the potentiometer |03. This potentiometer is connected between the +B terminal of a direct current source and ground. The rectifying circuit of the ldiode |00 is completed throughresistor |04 which is connected between the cathode and ground.

Across capacitor |05 potentials are fed to the grid 06 of an inverter device which comprises the left section of a. twin triode tube |01. The grid control results from variations in the potential drop across the input circuit resistor |08 connecting the grid |06 with ground. 'Ihe phase inverter device has a cathode resistor |09 connecting the cathode with ground and this resistor is shunted by a capacitor I0.

The output from the phase inverter section of tube |01 is fed to grid of the right hand triode section of this tube. The grid control potentials are reflected in variations of potential drop across the input circuit resistor H2, these variations being produced by coupling the anode of the phase inverter device to the grid across capacitor H3. The two anodes in tube |01 are fed with +B potential across resistors I4 and I l5 respectively.

A saw-tooth wave is delivered as output energy from the right hand section of tube |01 and is modified by a clipper device consisting of the diode tube 6 and associated circuit connections. The cathode of tube ||6 is coupled to ground across capacitor ||1 and is conductively connected to ground through a potentiometer H8, the latter being disposed across the terminals of the +B source. l

As is well understood by those skilled in the art, tube IIB operates to clip the peaks of the saw-tooth wave by a suitable amount so that the slope of the saw-tooth wave shall extend only through one-third of the scanning cycle. This slope of the wave is utilized for beam deflection, while the horizontal portion of the wave is coextensive with the blanking operation applied to the cathode i6 in the put-onfgun of the tube I0.

The deflection potentials represented by the Y utilizable slope of the saw-tooth wave are coupled across capacitor i9 to the control grid of an amplifier tube |20. This tube is preferably of the pentode type and its circuit connections are con- 11 ventional. The grid resistor |2| is shown connected between the control grid |22 and ground. The output circuit for tube |20, having conventional components, is coupled across capacitor |23 to one of-the deectingplates 22 in the put-on" section of tube I0.

It vwill be understood from the foregoing description that deflection is produced by the opposing electrostatic plates 22 such as to scan the target in one-third of the distributor cycle. During the remaining two-thirds of this cycle the beam is blanked out. A centering adjustment for the beam deflection is obtained by means of a potentiometer |24 and the impedance |25 which is connected between the tap on this potentiometer and the lead to the ungrounded defiecting plate 22. Suitable adjustment of the biasing potential applied to this plate is, therefore, obtained by connecting the terminals of the potentiometer |24 between points of fixed direct current potential, which may, for example, be considered as having the values +50 volts and -50 volts when referred to a zero-volt ground potential.

, A circuit comprising the twin triode tube |26 is provided for suitably blanking the put-on Ibeam so that an individual tube will function only with respect to the signals of a particular multiplex channel. The control of the left hand section of tube |26 is derived from the output circuit in the right hand section of tube |01. That is to say, a derivative of the saw-tooth wave produced by this right hand section of tube |01 is applied to the control grid on the left side of tube |26.

The two triode sections of tube |26 in combination serve to produce a square wave derivative of the clipped saw-tooth output from the generator |01. The right hand section of tube |26 is controlled by the left hand section and its cutoif condition persists during two-thirds of the cycle corresponding to the truncated portion of the saw-tooth wave. The right hand section of tube |26 is also conductive during one-third of the cycle corresponding to the slope of the sawtooth wave. During this one-third cycle, a negative pulse is fed across capacitor |21 so as to bias the cathode I6 in the cathode ray tube more negatively. The put-on gun, therefore, functions in phase agreement with the beam deection. The more positive bias which is applied to the cathode I6 during the remainder of the cycle acts to blank out the signal portions which are in tended for other put-on guns in cathode ray tubes corresponding to the other intelligence channels of the multiplex system.

In the immediately preceding paragraphs the signal effects are shown to be applied to the put-on beam in a given tube I0 for a single channel. After suitably delaying the synchronizing impulses so as to produce phase displaced operations in the other cathode ray tubes I0 of the receiver, the same functions are performed for reception of the signal trains appropriate to the other channels. The phase relations between the different groups of apparatus for channel A, channel B, and channel C have already been ex-l plained with reference to Fig. 4. It remains, however, to point out the details of phase control as shown in Fig. a.

The means for producing a 60 delay in the start of the scanning sweep of the take-off beam, relative to the start of the scanning sweep of the put-on beam in the same cathode ray tube comprises a multivibrator tube 96. This tube is prefl2 erably oi' the twin triode type. Associated with its input and output electrodes are the usual time constant impedance. together with cross-coupling capacitors, whereby a rectangular wave is produced in response to the synchronizing impulses. The phase relation between the input and output is adjusted to the desired angle, namely, 60. The potential on the anode 53 rises and falls cyclically and delivers control pulses across capacitor 63 and the input circuit resistor 66 for the left triode section of the twin triode tube 91. This side of the tube functions as a phase inverter. It is resistance-coupled to the right triode section of the same tube, the latter having for its function to generate saw-tooth waves for controlling the scanning action of the take-oil beam. The saw- Y tooth wave potentials are coupled across capacitor to the grid of a beam power amplifier tube 98. This tube may be of the same type as tube in the transmitter, and may be provided with corresponding circuit components. Hence, the latter are given like reference numerals and need not be further described. After amplification by the tube 98. the sweep circuit potentials are applied to the deflecting coils 30, as shown in Fig. 5.

The multivibrator device 99h operates under control of output pulses from the similar device 96. The circuit parameters are similarly chosen for producing a further delay amounting to in the output component of the synchronizing pulses. The result is that the output pulses from the multivibrator 99h are delayed by 120 with respect to the synchronizing signals issuing from the radio receiver.

The synchronizing pulse delay functions which are performed in successive stages by the multivibrator units 99h, 96h, 90e, and 96C are such as to maintain proper phase relations between the different beam scanning operations, also between the blanking operations in the cathode ray tubes for channels B and C. The overall channel time is, therefore, suitably divided between the three channels. Separate responsive devices for each channel are served exclusively with the intelliv gence signals appropriate thereto.

It will be understood, of course, that modifications of my invention may be made in many ways without departing from the spirit of the invention. The number of intelligence channels to be multiplexed need not necessarily be three, but may be any practical number of channels from two up. Only the phase relations between the cyclic operations of the different cathode ray scannings need be changed if a four-channel system were to be substituted for a three-channel system for example.

One of the advantages to be derived from the useo! my invention, particularly if it is to be worked for radio telephony, is that the modulations as transmitted are at frequencies so much greater than the normal voice frequencies as to be practically` unintelligible to an unauthorized recipient. The scrambling of these multiplied modulation frequencies as derived from the diiferent channel sources adds further to the secrecy characteristics of the system. I am acquainted with secrecy systems of the prior art which use multiplied or divided modulation frequencies, but, so far as I am aware, I am the first to disclose a multiplex distributor which inherently operates as a modulation frequency multiplier at the transmitting station, and as a modulation frequency divider at the receiving station.

It will be appreciated by those skilled in the art that in practicing my invention I am not 13 limited to the use of cathode ray tubes having the precise constructional arrangements shown in the aforementioned application of Iams yet al. Other cathode ray tubes are known which employ two electronic guns. Some of these are designed to project electron beams from opposite sides of the screen. For example, Iams Patent No. 2,269,588, issued January 13, 1942, shows a cathode ray tube of that type. It is apparent, therefore, that one of the guns in such tube might be used as the put-on gun, while the other gun is used as a take-01T gun.

It is also well within the scope of my inven-v tion to'use a cathode ray tube similar to an Iconoscope which would have a standard mosaic and which would employ a second gun directed at the same face of the mosaic. In this case the "put-on and take-olf beams are caused to strike successively the same spot. The differentiation between the put-on and take-off beam a-ction is obtained by the use of high velocity and low velocity beams respectively. As previously explained, the high velocity put-on beam produces secondary emission which accumulates variable positive charges on the screen. These charges are removed by the low velocity take-oil beam.

Still another modification of my invention may be practiced by those skilled in the art by the adoption of cathode ray tubes having means embodied therein for rotary scanning of the beams. 'I'hus it is well known that by maintaining two beam deflection potentials in a 90 phase relation one to the other, scanning in a circular path may be obtained. The screen in this case may also be of the standard mosaic construction used in Iconoscopes, if desired.

Various other modifications of my invention may also be made without departing from the spirit thereof.

I claim:

l. A multiplex communication system comprising a plurality of electron discharge tubes each appropriate to a diierent multiplex channel, a common transmission medium coupled to said tubes, each said tube containing a single storage screen having a multiplicity of parallel conductors, each tube also containing two cathode ray guns each arranged to project an electron beam toward said screen for scanning said conductors in a ratio greater than unity, one of said guns emitting a high velocity beam which stores the signal on said storage screen, the other of said guns emitting a low velocity` beam which takesoi the stored signal, a beam d-eecting device associated with each gun, a saw-tooth wave generator for actuating each one of said deecting devices, means for synchronizing the scanning strokes of said beam delecting devices while maintaining phase displacements therebetween, and means including delay circuits coupled to said common transmission mediumA for causing the scanning stroke produced by one deflecting device in each tube to be completed in a fractional part of the continuous scanning cycle effective forethe other said deflecting device in each tube.

2. A multiplex communication system comprising an electronic storage device individual to each channel, each said device including a scanable screen-like array of linear conductive elements of a single electrostatic target, means in said device for emitting a signal-modulated electron beam and projecting said beam toward said target at such high velocity as to cause secondary emission from said target at the focal point of said beam, means for cyclically deecting said beam transversely across said linear conductive `elements, means for collecting the secondary electrons released by said beam, thereby to eiect the storage of positive charges on dilerent ones of said linear conductive elements of the target corresponding to the modulation characteristics of a portion of a signal train, a low velocity electron beam emitting means for successively removing the stored positive charges from different parts of said target, and means operablein synchronism with the cyclic scanning rate of said storage device for deecting the low velocity beam in such manner as to alter the modulation frequency range of the stored signals and to deliver the same to a utilization device.

3. In a multiplex distributor which terminates signal channels in a multiplex communication system, a plurality of cathode ray tube devices each individual to a respective multiplex signal channel, each said device comprising an electronic put-on gun and an electronic take-off gun. said guns being adapted and arranged to emit high velocity and low velocity electron beams respectively,` beam deecting means individually associated each with a gun, asingle target screen in each said device arranged to be scanned by both of its beams, .said target being composed of a multiplicity of elemental electrostatic plates insulated one from another, a single plate separated from said elemental plates by a dielectric, an amplifier under control of potential charges removed from all of the single plates of the several cathode ray tube devices in accordance with the scanning action of said low velocity beams, and means for effecting sequential scanning operations in respect to the different low velocity beams whereby the signals simultaneously and continuously stored by the different high velocity beams are successively taken 01T for each signal channel at mutually exclusive time intervals, the modulation frequencies of said signals being multiplied for the purpose of substantially distortionless multiplex transmission.

4. In a multiplex distributor which terminates signal channels in a multiplex communication system, a plurality of cathode ray tube devices each individual'to a respective multiplex signal channel, each said device comprising an electronic put-on gun and an electronic take-oir gun, said guns being adapted and arranged to emit high velocity and low velocity electron beams respectively, beam deflecting means individually associated each with a gun, a target in each said device arranged to be scanned by both of its beams, said target being composed of a multiplicity of elemental electrostatic plates insulated one from another, a single plate separated from said elemental plates by a dielectric, a plurality of ampliers each individually controlled by a respective one of said single plates in accordance with the, scanning action of the take-off gun in a corresponding cathode ray tube device, means for blanking out the control of each put-on gun during the reception of signals other than thoseappropriately assignable thereto, means for maintaining synchronism between the several scanning actions effective upon the different beams, means including delay circuits coupled to the common circuit of said multiplex system for sequentially operating the v to said common circuit for operating the "takeott scanning f operations for the diiferent channels sequentially and substantially continuously.

5. In a multiplex communication system 'hav- I ing signal storage means of the type wherein capacitive charges are stored on and taken oil.' from a multiplicity of target elements in a cathode ray tube and a separate cathode ray tube is provided for each multiplex channel, the method of multiplexing which comprises impressing'the moduv lations of diilerent trains of signals respectively signal storage means of the type wherein capac itive charges are stored on and taken of! from a multiplicityof .target elements in a cathode ray tubea separate cathode ray tube being provided for each multiplexchannel, and each cathode rayl tube having two electron guns therein, one

for emitting af'put-on beam and the other for emitting a "take-oi!" beam, the method of distributing multiplex signals'to ditl'erent channel receivers which comprises modulating the puton" beams oi' the diiferent cathode ray tubes intermittently and in such manner that each beam stores on its target elements only that portion of the signals which is appropriate to a single channel of said multiplex system, blanking the action of each said beam during portions of the scanning cycle which pertain to other channels, producing continuous scanning excursions in each tube so as to "take-off the stored charges from the diiferent target arrays therein, and feeding the channel-separated signals to said receivers separately in accordance with the respective continuous scanning excursions.

7. In a multiplex communication system, a double-gun cathode ray tube for each channel, each tube having a high velocity put-on" gun Y in combination with means for deilecting its beam 16 .y such that a common output circuit for the nultiplex system may be fed with signals derived from the different take-oil" scanning operations successively and at mutually exclusive times.

8. In a multiplex communication system. a

double-gun cathode ray tube for each channel, each tube having a high velocity "put-on" gun, a "take-oi!" gun in each said tube operable at a low velocity of emission. and means including sawtooth wave generators for deilecting the beams of .the dinerent "take-oi!" guns so that theirsweeps are sequential and occupy mutually exelusive portions of the scanning cycle.

9. The combination according to claim 8 and including4 blanking means operable upon the beams of the v'clin'erent put-on guns in such manner that each gun functions to store signals appropriate to a respective one of the multiplex channels. y

l0. The combination according yto claim 8 and including a saw-tooth wave generator and clipper device for separately controlling said deiiecting means which are individual to the different puton guns.

11. In a multiplex communication system,l a double-gun cathode ray tube for each channel, each tube having a put-on" gun, a take-oi!" gun in each said tube, and means including sawtooth wave generators for deiiecting the beams of the diilerent "take-oi!" guns so that their sweeps are sequential and occupy mutually exclusiveportions of the scanning cycle. f

12. A multiplex system for the transmission and reception of a plurality of simultaneously A originated telephone signalsand the like, said system comprising cathode ray tube signal Istorage means at points of transmission and reception, 'means `utilising signal storage means to render the multiple storage oi' signals continuous at the point'of transmission, cathode ray tube scanning means at the point of transmission for. frequency-multiplying the signal waves, said scanning means being also effective to compress said waves'into distributive time intervals which are individual to the different multiplex channels, a plurality of cathode ray tube signal storage units at the point or points of reception, each said storage unit comprising a cathode'ray tube and a low velocity take-'otl" gun in combination with means for deilecting its beam intermittently a andduring times allotted to a single channel, a

target in each tube arranged to be scanned by the beams emitted from both of said guns, said target being composed of a plurality oi.' paralleldisposed linear conductors insulated one from appropriate to each of the multiplex channels, means in each said receiving tube for selecting the discrete portions of the multiplexed incoming signal wave train which are appropriate to a given one of the multiplex channels and for suppressing the etlects of other channel portions of said train, and electron beam deecting means for frequency dividing the selected signal wave portions and for expanding the same so that their original continuity is restored.

13. In a multiplex system, a nrst vacuum tube comprising an envelope having an electron receiving target and apair of electron guns, means for causing said guns to scan said target at dii'- 'ferent speeds and at a predetermined phase relation other than zero, a source of signals for modulating the electron beam emanating from one of said guns, a second similarly constructed storage on said target and complete release there-L' vacuum tube having in circuit therewith means for causing the guns thereof to scan its target at different speeds and at a predetermined phase relation other than zero, and another source of signals' for modulating the electron beam emanating from one of the guns of the second tube, a generator, and connections from said generator for synchronizing the operation of both said vacuum tubes at a phase relation other than zero.

17 14. A system in accordance with claim 13, including a common output circuit coupled to the targets on both tubes.

15. An electronic distributor for multiplex communication systems comprising means for utilizing a communications channel in such manner.

that each signal train in its entirety is divided into discrete channel time units, each unit comprising a frequency-multiplied and compressed portion of said train, means for allocating the channel time units to the diierent multiplex channels in successive order, multiple means including cathode ray tubes of the double gun type for segregating and storing diierent portions of the multiplexed signals which are appropriate to each channel, including other cathode ray -tubes of the double gun type for expanding said signals after reception and storage thereby to restore their original frequency characteristics and continuity.

16. In a multiplex communication system, a double gun tube for each channel, each tube having a. put-on gun and a take-off gun, means including sweep circuits individual to said tubes for deecting the beams of the diierent take- 18 oi guns andincluding delay circuits between the diierent channels for assuring that the sweeps of said sweep circuits are sequential and occupy mutually exclusive portions of the scanning cycle.

17. In a multiplex communication system, a. double gun tube for each channel, each tube having a put-on gun and a take-off gun, means including sweep circuits individual to said puton guns for deecting the beams of the different put-on guns in overlapping time durations, and other sweep circuits individual to said takeoff guns for deecting the beams of said take- 01T guns in mutually exclusive time durations.

MAX H. MESNER.

REFERENCES CITED The following references are of record in the le of this patent:

UNITED STATES PATENTS Number Name Date 2,191,565 Henroteau Feb. 27,-1940 2,277,516 Henroteau Mar. 24, 1942

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