GB553393A - Receiving systems for simultaneous communications occupying a wide frequency band - Google Patents

Abstract

553,393. Multiplex transmission. STANDARD TELEPHONES & CABLES, Ltd. (International Standard Electric Corporation.). Feb. 27, 1942, No. 2594. [Class 40 (iv)] A set for receiving a number of carrier channels comprises scanning means for deriving from each active channel a train of equally spaced pulses of demodulated side-band. These pulses may be used merely for the control of a cathode-ray oscillograph to indicate which channels are active or they may be fed together to a number of channel receivers which are normally inactive but are activated momentarily in turn by pulses synchronous with the pulses of demodulated side band so that each receiver receives only 'the pulses of its own signal. As shown, a scanning generator 29 varies the frequency of the demodulation oscillator in the receiver 23 continuously or in steps and also controls a pulse generator 30 for unblocking channel receivers 24/1 .. 24/n in turn. The two sets of pulses are brought into the proper phase relationship with the aid of a cathode ray tube 32, which gives an indication along a horizontal scale for each active channel, and a cathode ray tube 31, controlled by the same time-base voltage, which shows the unblocking pulses. These are adjustable in phase with the aid of individual delay networks. Alternatively, the unblocking pulses may be produced from the side-band pulses with the aid of photo-electric cells acted on by the oscillograph 32. The tuning adjustment may be effected mechanically as by rotating a condenser or electrically, e.g. by an electronic or mechanical switching arrangement.