Patent GB-604130-A (GB)
Title: Improvements in or relating to electric pulse communication systems
IPC: H04J3/06
Filed: 1945-01-03
Abstract: 604,130. Pulse multiplex signalling. STANDARD TELEPHONES & CABLES, Ltd., CHATTERJEA, P. K., and HOUGHTON, L. W. Jan. 3, 1945, No. 308. [Class 40 (v)] In a multiplex signalling system in which the channels are carried by intercalated pulse trains forming a combined pulse train, the latter is modulated in accordance with a synchronizing wave independently of the normal . modulation of each channel by its own signals. The types of modulation used for the synchronizing signal and the channel signals may be. different. For example the channels may be time-phase modulated and the synchronizing signal time-duration or amplitude modulated, or other combinations may be used. In one embodiment, at station 1, a master oscillator 9 operating at the pulse recurrence frequency of each channel controls a pulse generator 10 feeding delay devices 11 ... 14, which may be of the type described in Specification 593,482, for four channels.' A fixed delay in these devices separates the channel trains and in addition the delay time is modulated by signal sources 15 ... 18. The channel outputs are mixed at 19 and fed through a further delay device 20 to the outgoing circuit or radio link 7. The synchronizing signal is provided by applying the output of master oscillator 9 directly to modulate the delay time of device 20 through which the combined pulse train is passing. At the receiver at station 2, a local pulse generator 23 is controlled by the received synchronizing signal separated by the bandpass or low-pass filter 22. The gate circuits 28 ... 31 receive the combined signal input over line 32 and pulses from the generator 23 with different delays introduced by networks 24 ... 27 for channel separation. Individual channel demodulating circuits 33 ... 36 are fed from the gate circuits. In the two-way system shown, the pulse generator 23 also controls the station 2 transmitter and produces the pulse trains for the outgoing pulses modulated by signal sources 15A .. 18A in the delay devices 11A ... 14A. The receiver at station 1 is similar to that at station 2 but the pulses for channel separation in the gate circuits 28A ... 31A are derived from the transmitter pulse generator 10. In a modified form of transmitter for station 1, Fig. 2 (not shown), individual pulse generators are provided for each channel being fed from 'the master oscillator through fixed phase changing circuits so set that their outputs are, in effect, time modulated by the synchronizing signal as in Fig. 1. The channel modulating signals are applied direct to the pulse generators. In a further modification, Fig. 3 (not shown), the phase changing networks produce merely the normal channel separation of the pulses generated, and the synchronizing signal modulation is introduced by subsequent preset delay networks. In this embodiment the resulting synchronizing signal modulation can be different in form from the waves from the master oscillator. When these modified transmitters are used at station 1, a separate pulse generator is provided which is controlled by the transmitter master oscillator and feeds the receiver over line 42, Fig. 1. If they are used at station 2 the master oscillator is omitted and its place taken by the synchronizing wave from filter 22, Fig. 1, fed over connection 51.