GB895983A - Improvements in selective electrical switching arrangements - Google Patents

Abstract

895,983. Automatic - exchange systems. BRITISH TELECOMMUNICATIONS RESEARCH Ltd. May 5, 1960 [May 15, 1959], No. 16739/59. Class 40 (4). A cross-point switching arrangement comprises a co-ordinate matrix of semi-conductors, one of which is rendered operative by row and colunm markings applied to two electrodes thereof to energize an associated relay. In Fig. 1, transistors such as TR are employed, positive " row " pulses being applied to the emitter by way of relay coils RC and negative "column" pulses to the base. When the transistor conducts, a high value capacitor C1 is charged from a floating power supply, which may consist of a second high value capacitor C2 fed with rectified A.C., and provides current for the operation of relay RC, as long as the pulse repetition rate is sufficiently high. The relay is preferably of the dry reed type. Instead of transistors, crystal diodes may be used and these may be associated with transistors acting as amplifiers. In a 100-line exchange the subscribers' lines would be arranged in columns divided into two halves for the calling and called sides of a connection, the rows in the two halves being connected in pairs to form transmission bridges. The marking pulses may be obtained from single-shot multi-vibrators, Figs. 3, 4 (not shown), under the control for instance, of a magnetic drum register.