Patent GB-596700-A (GB)
Title: Improvements in or relating to two-way electric pulse communication systems
IPC: H04B1/46
Filed: 1945-12-31
Abstract: 596,700. Multiplex pulse signalling. STANDARD TELEPHONES & CABLES, Ltd., and LEVY, M. M. Dec. 31, 1945, No. 35317. [Class 40 (v)] In a two - way multi-channel pulse communication system in which each terminal equipment comprises a transmitter and a receiver for intercalated trains of channel pulses, means are provided for synchronizing the two equipments so that each pulse received by each of the equipments is interleaved between two pulses transmitted by the same equipment. In one embodiment, a plurality of pulse modulators 15A, 15B ... 15L, 15M, Fig. 4, are arranged in a series alternately with pulse demodulators 16A, 16B ... 16L, 16M. The distributer 10 supplies pulses in turn to the modulators and demodulators in alternate periods from the master pulse generator 9. At the co-operating station the pulses from generator 9 are replaced by synchronizing pulses supplied over lead 14 from the receiver. The demodulators are all connected to the radio receiver 5 and receive the combined incoming trains of channel pulses, each picking out its own channel pulses by means of the gating pulses from the distributor 10, the demodulated signals being taken from terminals 18A., 18B ... 18L, 18M. The receiver 5 is blocked by each transmitted pulse over a lead 12 from the radio transmitter 3. The pulse modulators fed with modulating signals from terminals 17A, 17B ... 17L, 17M. and the demodulators may be of the type described in Specification 596,658. The distributer may comprise a delay network as described in Specification 587,939 and consisting for example, of 200 sections each introducing a delay of 0.5 microsecond, with a tapping available at each section, in the case where ten two-way channels are provided. This enables switching to be provided, so that, when the pulse period is changed by adjustment of generator 9 to fit the inter-station transmission period, suitable changes may be made in the distributer delay periods up to a maximum of 10 microseconds for the twentieth channel, Fig. 5 (not shown). Another type of distributer requiring no mechanical adjustments when the pulse repetition frequency is changed is similar to that described in Specification 596,699, which comprises a chain of pulse generators A1, A2, B1, 132 ... M2, Fig. 6, one for each out going and incoming channel. The first pulse generator A1 is triggered once per complete cycle of channel operation from a frequency divider 28 fed from generator 9 or incoming synchronizing signals. The other channel pulse generators are triggered by the terminating pulse from the preceding generator in the chain. Each generator is returned to quiescence by the next pulse from the master source following the triggering pulse. The generator A1 has the pulses from divider 28 applied to the grid of a gas-discharge triode 29 and pulses from the master source are applied to the grid of a second gas-discharge triode 30. Anode voltage for valve 30 is derived from the cathode resistor 35 of valve 29 across which the gating pulses are developed and fed to terminal 25. In the quiescent state, both valves are non-conducting and condenser 34 between the anode of valve 29 and H.T.-, is charged to full H.T. potential from terminal 31. The input pulse causes valve 29 to conduct, partially discharging condenser 34 and providing H.T. voltage for valve 30 across resistor 35. The next pulse from the master source renders valve 30 conducting and condenser 34 discharges through valves 29 and 30, to extinguish valve 29 and remove H.T. Voltage from the anode of valve 30 which is also therefore extinguished. The circuit is then quiescent again until re-energized by a pulse on the grid of valve 29.