GB638371A - Multi-channel communicating system - Google Patents

Abstract

638,371. Pulse modulation; multiplex radio signalling. STANDARD TELEPHONES & CABLES, Ltd. June 6, 1947, No. 14992. Convention date, March 5, 1945. [Class 40 (v)] In a multi-channel receiver for time-modulated pulses, synchronizing pulses S (Fig. 2A) are delayed (Fig. 2C) to overlap the pulses of the respective channels and are shaped with linearly sloping tops (Fig. 2D), and combined with the signal pulses, the combined wave for each channel being clipped above a predetermined level so as to give amplitude-modulated pulses (Fig. 3, not shown). The pulses, received by line or radio, are fed to a clipper amplifier 8 (Fig. 1) operating between two limits 9, 10 (Fig. 2A), the resulting interferencefree pulses then being fed to a synchronizing pulse selector 11. This feeds the synchronizing pulses to a delay network 13, the delayed output of which is fed to the shaper 16, the synchronizing and signal pulses being combined and clipped in a selecting demodulator 18. The amplitude-modulated pulse output of the demodulator 18 is fed to a low-pass filter 20 and telephones 21. Shaping of the synchronizing pulses may be effected by a transformer (Fig. 1), a differentiator circuit, a multivibrator, or by combination of the synchronizing pulses with the output of a harmonic selector also fed by the synchronizing pulses (Figs. 4, 5 and 6, not shown). Specifications 600,291 and 638,345 are referred to.