GB690590A - Improvements in or relating to electric signal amplifier systems - Google Patents

Abstract

690,590. Multiplex pulse signalling; valve gating circuits. STANDARD TELEPHONES & CABLES, Ltd. March 16, 1951 [March 17, 1950], No. 6367/51. Classes 40 (v) and 40 (vi). In a system in which an amplifier is switched alternately to amplify signals passing in both directions between two circuits along a channel, means are provided to neutralize the effect of signals persisting in either of the circuits after the reception interval has ended. In one embodiment, the amplifier 50 is alternately connected between circuits 30 and 31 and circuits 31 and 30 by the switching voltage produced by a multivibrator 33. The terminals 34, 35 of the latter are alternately raised to a positive potential. When terminal 34 is positive, the pairs of rectifiers 42, 43 and 46, 47 are rendered conducting, so that the output of amplifier 50 is fed through condenser 52 and rectifiers 46, 47 to circuit 30 and its input is connected to circuit 31 through rectifiers 42, 43, condenser 51 and valve 48. When the other pairs of rectifiers are rendered conducting, circuit 30 feeds circuit 31 through the amplifier 50. The rectifiers are biased by batteries connected between earth and the points 36, 37, 38, 39, at which the pairs of rectifiers are connected together..To avoid cross-talk between a pulse passing from circuit 30 to circuit 31 and vice versa, and the residue of the preceding pulse passing in the opposite direction, each pulse from the amplifier is fed to a circuit 53 where its amplitude is appropriately changed and then through a delay circuit 54 to be subtracted from the succeeding pulse applied to the amplifier. For this purpose it is fed to valve 49, the common output circuit of valves 48, 49 being arranged to produce a pulse proportional to the difference in the inputs to the two valves. Two circuits such as 53, 54 may be provided, Fig. 3 (not shown), but with different delay times, so as to compensate also for pulses persisting for three times the period of the delay circuit 54. The system may be used for the transmission of multiplex pulse trains.