Patent GB-368330-A (GB)
Title: Improvements in multiplex signalling
IPC: H04J3/04
Filed: 1930-11-29
Abstract: 368,330. Thermionic distributers. COMMUNICATION PATENTS, Inc., 60, Broadway, New York, U.S.A. Nov. 29, 1930, No. 36065. Convention date, June 13. [Class 40 (v).] In a multiplex communication system in which independent signals such as voice, television, telegraphic signals are transmitted over a single channel, thermionic distributers are employed at the transmitter and receiver, each distributer comprising a plurality of valves rendered operative in cyclic order to associate corresponding signal sending and receiving apparatus. Fig. 4 shows the distributer equipment at one station. Valves 75 .. 80 are successively interconnected by output impedances 81 .. 86 and input impedances 87 .. 92. When the grid of valve 75 is momentarily made positive in any manner such as by short circuiting the grid battery, an impulse is impressed upon valve 76 which in turn impulses valve 77 and this operation is repeated throughout all the valves and continues so long as energy is supplied to the valves. Thus the valves are rendered operative in succession and signals impressed upon windings such as 95 are repeated through the winding 101 when the associated valve is operative. The speed at which the valves are operated may be varied by altering the bias or the coupling impedances 81 .. 86 which may be operated from a common control. In the modification shown in Fig. 6, the valves are operated in a manner similar but means are provided for ensuring synchronous operation. Fig. 6 shows the apparatus at the receiving station, the cyclic operation of the valves being initiated by applying positive bias to the valve 110 by the switch 132. Moreover coupling units 135 .. 140 are provided for controlling the time delay of the impulses. The received signals which are distributed in the valves are also impressed upon a transformer 151 of a synchronizing arrangement 131. A resistance 153 connected in the grid circuits of the valves is shunted by the secondary winding of transformer 151 and a rectifier 152 and also by a similar secondary circuit of a transformer 154 connected to further windings on the output transformers 124 .. 129. The effect of the signals in transformer 151 is to modify the grid bias of the valves and thus alter the speed of operation, but this is neutralized by transformer 154 if the output impulses are in exact time relationship with those being received. If this system is completely out of step, it may be stopped and restarted by key 132. In a further modification grid bias may be substantially eliminated by the provision of a feed back transformer for each valve which is adapted to render the valve inoperative after the transmission of an impulse therethrough. The Specification as open to inspection under Sect. 91 (3) (a) describes also a thermionic distributer wherein the valves are rendered operative in cyclic order by polyphase currents derived from a separate generator. The generator comprises coils arranged in quadrature on a magnetic circuit to produce a rotating field which inacts with polyphase connected secondary windings. This subject-matter does not appear in the Specification as accepted.