US2275224A - Multiplex communication system - Google Patents

Description

R .J. VA

F. C. P. HENROTEAU MULTIPLEX COMMUNICATION SYSTEM March 3,1942.

Filed March 5, 1941 Patented Mar. 3, 1942 UNITED STATES PATENT OFFICE Francois Charles Pierre Hcnroteau, Ottawa, I v Ontario,-Canada Application March 5, 1941, Serial No. 381,906

g In Belgium March 6, 1940 3 Claims.

This invention relates to multiplex communication systems and is a development from the apparatus described in my prior United States application Ser.No. 252,030 filed January 20, 1939.

The system of the present invention comprises a central station and a number of substations so arranged that wireless communication may be had simultaneously and on the same wave length between the central station and all or some of the substations, and it may be used for example in a naval or aerial squadron to permit communication between the squadron commanders unit and other units.

The underlying idea of the invention is that may be synchronizedand that the selection by a substation of the signals intended for it or the transmission from that station of a signal for the central station without overlapping with signals prises a central station including an envelope operations at the central station and substations containing a number of mosaics (the term mosaic meaning wherever used in this application an assembly of the type used in many television systems and consisting of a multiplicity of mutually insulated tiny conductive electron emissive elements and a uniformly conductive backing layer, the elements and this layer often being carried on a central dielectric plat-e), means for scanning said mosaics simultaneously by different slow moving electron releasing beams and means for scanning said mosaics successively by a single fast moving electron releasing beam in a time no greater than that elapsing during the scanning of one mosaic by one of the slow moving beams, and a number of substations no greater than the number of mosaics at the central station and each including an envelope. the envelope at each different substation containing onlya single mosaic corresponding in position to a different mosaic at the central station. means for scanning each single mosaic by a slow moving electron beam synchronously with the scanning by the slow moving electron beams at the central station, and means for scanning each single mosaic by a fast moving electron beam synchronously with the scanning of the mosaic at the central station with which it corresponds in position by the first mentioned fast moving electron beam. The central station and each substation preferably includes a transmitter and a receiver so that two way communication is possible. In such a case an envelope forms part of each transmitter and each receiver. In the transmitter each slow moving electron beam is modulated by beams reconstitute the message or messages from the record or records so formed, In order to prevent beats due to phase displacement of the carrier wave coming in to the receiver at the central station simultaneously from the emitters at a number of central stations. means are preferably provided at each of the latter to prevent transmission of the carrier wave except while it is modulated by a message. The invention will now be described in more detail by reference to the accompanying drawing of one suitable form". In the drawing-- I Figure 1 is the transmission at the central station;

Figure 2 is the receiver at the central station; Figure 3 is the receiver at a substation, and Figure 4 is the transmitter at a substation. The transmitter of Figure l is similar to the transmitter shown in Figure l of my prior application and comprises an envelope I containing three mosaics 4. 5 and 6 having a common central dielectric p ate 3 and a common conductive backing connected through an appropriate amplifying and modulating device I4 to an emitting antenna l5. Associated with the mosaics is a conventional electron gun I housed in a pocket in the envelope. At the other end of the envelope and facing the mosaics is an electron emissive plate 8 which has three electron guns 94. 95 and 96 associated with it, each including a modulating electrode l0 connected to, for example, a microphone Between the plates is an accelerating electrode !2 and inside the envelopean electronic lens in the form of a coudensive coil IS.

The receiver of Figure 2 is similar to the transmitter of Figure 1 but with the'clccf-ron guns reversed and the conductive bookings of the mosaics separate. Thus. electron guns l4. l5 and 16 are associated with the mosaics 4|, 5| and BI respectively and the conductive backing of each mosaic is connected through an appropriate amplifying device 18 with, for example, a pair of earphones l9. On the other hand one electron gun 9 is associated with the plate BI and its modulating electrode I is connected through an appropriate demodulator and amplifier IS with areceiving antenna 11.

At each substation the transmitter may .be identical with the transmitter at the central sta tion except that there is only one mosaic and only one electron gun associated with the electron emissive plate. Figure 4 shows the transmitter for one substation. Here there is a mosaic 4a corresponding in position to the mosaic 4 in Figure 1,;and mounted conveniently on a plate 3a identical with the plate 3 in Figure 1 and there is one electron gun 94a, corresponding to the gun 94 of Figure 1, associated with the plate 8a identical with the plate 8 in Figure 1.

Similarly, the receiver at each substation may be identical with the receiver at the central station except that there is only one mosaic and associated electron gun. Thus in Figure 3; which shows the receiver for the substation of which the transmitter is shotm in Figure 4, there is Only a mosaic lla corresponding in position to the mosaic H of Figure 2, and an associated electron gun Ma. As in Figure 4, the mosaic is conveniently on a plate 31a identical with the plate 3! of Figure 2.

Each of the two other substations, which a system having the central station transmitter .and receiver of Figures 1 and 2 could include,

would have the same receiver and transmitter as those shown in Figures 3 and 4 except that the mosaics would correspond in position with the mosaics 5i and 5 and 4| and 4 respectively.

The system described operates generally as described in my prior application in connection with the contemporaneous transmission of a number of messages over a single transmission channel. In Figure l, the slow-moving electron beams from the guns S4. 95 and 98 are caused to scan simultaneously different areas of the plate 8 corresponding to the mosaics 4, 5 and 6 respectively, the intensity of these beams being modumosaic Ma. It thus leaves a record only of the signalling impulses corresponding to the message impressed on the beam of the gun 94 and recorded on the mosaic 4. The mosaic Ma is scanned by a slow-moving beam of electrons from the gun Ida synchronously with the scanning by the beam from the gun 94 and thus reconstitutes the message which passes to the earphones. At the receivers of the other two sub- I stations only the messages recorded on the mosaics 5 and 6 respectively are reconstituted. Thus although all the messages are sent on the same wave length from the central station, each substation efiectively receives only the message intended for it.

In a similar way in the transmitter of Figure 4, a slow-moving beam of electrons from the gun 94a. modulated in accordance with the message to be sent to the central station scans an area of the plate 8a corresponding to the area of the plate 8 scanned by the beam of the gun 94 synchronously with that beam, and so produces a slow-moving beam of secondary electrons which scans the mosaic 4a and records the message on it. The record on the mosaic is translated into signalling impulses by the fast-moving beam from the gun 7a scanning the mosaic synchronously with the scanning by the beam from the gun l at the central station. At the transmitters at the other substations scanning proceeds. synchronously with the scanning in the transmitter of Figure 4, but these other substations have only mosaics corresponding in position to the mosaics 5 and 6 respectively at the central station with the result that the formation of signalling impulses begins for example in the secondsubstation only after such formation has -.at the receiver of the central station picks up successively the signally impulses coming from lated by the modulating electrodes ID in accordance with messages to be transmitted. When one of the beams 94, 95 and 96 strikes the plate set of earphones is through the amplifiers It.

these beams causes beams of secondary electrons moving beam of electrons from the gun I in a time at the most equal to the time taken for one scanning of a mosaic by the above mentioned beams of secondary electrons. and this scanning converts the records into signalling impulses with which a carrier wave is modulated and transmitted. At the substation shown in Figure 3 the receiving antenna picks up all the signalling impulses transmitted from the central station, and the intensity of the fast-moving electron beam from the gun 9a. which. scans the plate 8la synchronously with the scanning of the plate 3 by the beam from the gun I at the emitter, is modulated in accordance with them.

The arrangement shown in Figures 3 and 4 where the mosaics 4a and Ma are on plates identical respectively with the plates 0 and 3! struction of the apparatus. since an easy way is There is thus produced a beam of secondary electrons of variable intensity which scans the plate 3|a but leaves a record only during a part 0! this scanning, namely, when it traverses the mission from the antenna l5a except when sig- I nailing impulses are being produced in order to prevent at the receiver the beats which would otherwise be caused by phase. displacement between the waves received from the different substations. A convenient arrangement for this purpose is shown in Figure 4 where the conductive backing for the mosaic 4a is connected to the filament 20 of a three electrode tube 2| to the plate 22 of which the antenna is connected.

cathode ray oscillograph 25 containing a plate I 26 having an electron emissive area 21 having the same relative position on the plate as the mosaic 4a on the plate 3a. The plate is scanned by a beam of electrons synchronously with the scanning by .the beam from the gun la. When the surface 21 is scanned there is an emission of electrons which being picked up by the anode 24 causes the grid 23 to acquire a potential such as to allow passage of current through the tube 2l but when the rest of the surface 26 is scanned the potential of the grid 23 is such as to block any passage of current and thus prevent transmission from the antenna l5a.

The invention has been described with relation to one particular form of construction but it will be understood that it is not limited to form thus for example, it can perfectly well be used with the alternative form of construction shown in my prior application referred to. Moreover, it is not essential that scanning of the mosaics by the slow moving and fast moving electron beams proceed simultaneously since this might be effected alternatively as indicated in my prior application,

What I claim is:

mosaic at the central station, means for scanning each single mosaic by a slow moving electron, The grid 23 is connected to an anode 24 of a beam synchronously with the scanning by the slow moving electron beams at the central station, and means for scanning each single mosaic by a fast moving electron beam synchronously with the scanning of the mosaic at the central station with which it corresponds in position by the first mentioned fast moving electron beam.

2. A multiplex communication system according to claim 1 in which at each substation the slow moving electron releasing beam is adapted to record a message On the single mosaic and the fast moving beam to convert the record into signalling impulses, comprising means for modulating a carrier wave by said impulses, and means for preventing transmission of such wave except 1. A multiplex communication system comprising a central station including an envelope containing a number of mosaics, means for scanning said mosaics simultaneously by different slow moving electron releasing beams and means for scanning said mosaics successively by a single fast moving electron releasing beam in a time no greater than that elapsing during the scanning of one area by one of the slow moving beams, and a number of substations no greater than the number of mosaics at the central station and each including an envelope, the envelope at each diiferent substation containing only a single mosaic corresponding in position to a different when so modulated.

3. A multiplex communication system according to claim 1, in which at each substation the slow moving electron releasing beam is adapted to record a message on the single mosaic and the fast moving beam to convert the record into signalling impulses, comprising means for modu-- lating a carrier wave by said impulses, and means for preventing transmission of such wave except when so modulated, said last mentioned means comprising a three electrode tube having a filament to which said carrier wave is fed, a plate connected to an antenna and a grid normally at a potential such as to prevent passage of electrons from said filament to said plate, and an auxiliary tube having an electron emissive plate in a position therein corresponding to the posi tion of the single mosaic in the envelope connected to said grid, and means for scanning said plate with an electron releasing beam synchronously with the scanning of the mosaic in the envelope at the substation by the fast moving electron releasing beam. FRANCOIS CHARLES PIERRE HENRO'I'EAU.

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