GB582979A - Improvements in or relating to time modulation pulse systems - Google Patents

Abstract

582,979. Pulse modulation. STANDARD TELEPHONES & CABLES, Ltd., and SHEPHERD, R. B. Sept. 11, 1942, No. 12875. [Class 40 (v)] Time-modulated pulses are derived by applying two separate synchronizing voltages, of pulse frequency and with a phase difference dependent on the signal voltage, to two saw-tooth generators ; the outputs being combined to produce the time-modulated pulses. As shown in Fig. 3, an oscillation O of pulse frequency is applied through a filter WF1 to one saw-tooth generator SG1, and through a phase-adjusting bridge network and filter WF2 to the other sawtooth generator SG2. The bridge network comprises two resistance arms R1, R2 and two reactance arms C1, C2 with the input and output connected across the respective diagonals. The resistances R1, R2 are thermally-sensitive, and may be variably heated either by passing the signal MS through heater coils r1, r2 or through the resistances themselves by applying the signal at the terminals O. In either case, the phase shift is proportional to the signal voltage. The phase-displaced saw-tooth voltages from the generators SG, SG2 are applied to the grids of valves Va, Vb, Fig. 5, and the time-modulated pulses are taken off across the two anodes at the terminals 5, 6. Two phase-displacing networks may be provided, controlled in opposite sense by the signal voltage. The thermal resistances in the respective networks may have temperature coefficients of opposite sign. In a modification, the resistances R1, R2 are normal resistances, and the phase shift is effected by connecting across one of the condensers C1, C2, the grid circuit of a valve operating by the Miller effect, the signal being applied after rectification to vary the apparent capacity by varying the grid bias (Fig. 4, not shown).