GB841555A - Improvements in or relating to transmission systems - Google Patents

Abstract

841,555. Automatic exchange systems. POSTMASTER GENERAL. July 13, 1956 [April 14, 1955], No. 10829/55. Class 40 (4). Two-way communication between two circuits X1, X2 of a group of such circuits is effected by providing each circuit with an integrating circuit WF1, WF2 and a switch S1 S2 connecting them to a common point H which in turn may be connected by a switch SL to one of a further group of integrating circuits CL, the switches S1 and SL being synchronously closed at one instant in a recurring cycle for mutual interchange of energy between WF1 and CL, and the switches S2 and SL being synchronously closed at another instant in the cycle for mutual interchange of energy between WF2 and CL. The recurrence frequency of the closure of switches S1 and S2 must be at least twice the frequency of the signals emitted from the sources X1, X2. The switches may be electronic gates pulsed by sources connected to the switches, Fig. 3 (not shown), or by sources connected in series with condensers C1, C2 of the integrating circuits. For improved transfer of energy inductances may be connected between the integrating circuits and their respective switches, the period of closure of the switches being half the resonance period of the circuits so formed. The condensers of the integrating circuits may be removed and low-velocity cable may either directly replace the condensers of the integrating circuits, or be inserted between the inductors and the switches. Fig. 7 illustrates an extension of the arrangement in which members of two such groups may be connected together, each group being provided with a common point H1, H2 connectable to the integrating circuit CL by switches SL1, SL2 which may be operated (in conjunction with an S-switch in each group) at different instants in the cycle. A suitable low impedance pulse source for the above embodiments may comprise a normally saturated inductor driven by a pulse on an input winding to the non-saturated state, thereby pulsing an output winding, Fig. 4 (not shown). The Provisional Specification describes an arrangement, Fig. 8, in which switches are connected in a closed loop. The voltage sources V1, V2 normally bias the rectifiers MR1, MR2 to conduction so that the outputs of the filters (or integrating circuits) WF1, WF2 are shortcircuited. If GX1 and GX2 are pulsed simultaneously the rectifiers are back-biased thereby effecting connection between the filters. Since in this case the inducatances L1, L2 of the filters are adjacent the switches, additional shunt capacities C1, C11 forming resonant circuits with the inductances may be provided, the half-resonant period being equal to the pulse period so that complete transfer of energy may be effected.