GB697127A - Multiple stable state electron-discharge tube circuits - Google Patents

Abstract

697,127. Pulse code modulation circuits; valve circuits. PHILIPS ELECTRICAL INDUSTRIES, Ltd. April 25, 1951 [April 28, 1950], No. 9632/51. Classes 40 (v) and 40 (vi). A trigger pair circuit comprising two crossconnected valves selects one of its two stable states in dependence upon a control voltage supplied to it and a common part of the grid circuits of the two valves is biased, so that they tend to pass equal anode currents, a generator producing rectangular switch pulses being connected in series with the bias source. Fig. 1 shows a trigger pair circuit comprising crossconnected valves 1, 2 in which bias source 9 has such a value that the valves are non-conductive except during the positive peaks of the switch voltage Us when one of the valves is rendered conducting and the other cut-off in dependence upon the control voltage Ui applied to the auxiliary valve 16 which is connected in parallel to valve 1. The diodes 12, 13 limit the positive grid swing of the valves 1 and 2 and the variation of the output voltage Ua with the value of the bias voltage Uo is dependent upon the value of the control voltage Ui, Fig. 2 (not shown). Fig. 3 shows the application of a trigger circuit comprising hexode 20 and triode 21 in a modulator for a pulse code modulation of the type described in Specification 684,318. The speech to be modulated is applied at Ui and appears amplified across resistor 34 and the output pulses from the trigger-pair circuit 20, 21 produced across resistor 40 are integrated in the anode circuit 31, 32 of valve 30. Thus a control voltage is applied to the second control grid of hexode 20 equal to the difference between the voltages across resistor 34 and the integrator circuit 31, 32, the value of this voltage determining which of its two stable states the trigger pair circuit will occupy during the positivegoing positions of the switch voltage Us. The output signal across resistor 40 is differentiated by network 41, 42 and passed to a receiver which may, for example, be as shown in Fig. 4. The incoming time-multiplexed code modulated pulse train is applied as a control voltage at terminal 43 to the hexode valve 20 of the trigger-pair 20, 21, which has a switching voltage Us applied to it, the pulse repetition frequency of which is equal to the channel repetition frequency in the incoming multiplexed signal. The pulses at the output of trigger valve 21 are integrated in the anode circuit 31, 32 of valve 30 to produce a replica of the original speech modulation, the pulse output of the trigger pair being independent of the shape or amplitude of the input pulse train at terminal 43 and of any noise components present in the input signal.