GB580769A - Improvements relating to pulse signalling systems - Google Patents

Abstract

580,769. Pulse modulation. STANDARD TELEPHONES & CABLES, Ltd., CHATTERJEA, P. K., and SCULLY, C. T. May 2, 1944, No. 8300. [Class 40 (v)] Signal-modulated electric pulses are produced by applying a repetitive wave of pulse frequency to render operative a normally inoperative oscillation generator of higher frequency, the tuned circuit of which is shunted by a unilateral conductor to suppress alternate halfcycles. The pulses thus produced are modulated in duration by varying the frequency of the oscillation generator ; or in time phase by varying the phase of the repetitive wave. As shown, the generator comprises a valve V1 with a tuned anode circuit L1, C1 back-coupled to the grid circuit and shunted by a rectifier D. The cathode is biassed by resistances r2, r3 so that the generator is normally quiescent, and is only rendered active at the peak input from a source S supplying waves of pulse frequency to the grid circuit. The generator produces a pulse in the form of a single half-cycle, the return half being suppressed by the rectifier. This pulse is shaped and limited by known means to a rectangular form. It is modulated in duration by applying the signal to the grid of a valve V2 which is connected across the tuned circuit L1, C1 and-functions by the Miller effect, or otherwise, as a variable reactance, thereby varying the frequency or period of the generator V1. In a modification (Fig. 2, not shown) the signal is applied to vary the phase of the source S thus producing a corresponding variation in the phase or timing of the pulse.