GB709327A - Improvements in receivers for voice-frequency telegraph transmission systems with amplitude modulation - Google Patents

Abstract

709,327. Code telegraphy. COMPAGNIE INDUSTRIELLE DES TELEPHONES. July 14, 1952 [July 20, 1951], No. 17702/52. Class 40 (3) In a voice frequency telegraph transmission system employing amplitude modulation and having an amplifier supplying current to a receiver relay provided with an operating winding and a compensating winding and in which the current through the compensating winding is proportional to the maximum current through the operating winding for a wide variation of the amplitude of the received signals, the intensity of the compensating current controls the attenuation of a network comprising a rectifier bridge arranged at the input. As shown in Fig. 2 the received signals are applied via an adjustable alternator 1 and amplifier 2 to a discriminator 3 which passes current to a main winding 4 and a compensating winding 5. The signals, rectified at 6 are applied to the winding 4 and over a rectifier 7 to the grid of a valve 8 via a network R1, Cl having a large time constant so that the bias of the grid of the valve assumes the general maximum value of the received signals. If the general level of the signals rises, increased current flow in the anode circuit of the valve 8 is fed back via resistance 13 to increase the attenuation of the network 12 so that the current flow through the main winding is reduced to a desired value. In a modification, Fig. 3 (not shown), the discriminator includes a second valve controlling the main winding 4 and having an R-C network with a small time constant so that the second valve responds to the voltage values of the signal elements. The two valves of this arrangement may be constituted as a doubletriode.