GB439323A - Improvements relating to automatic telephone and like selective systems - Google Patents

Abstract

439,323. Automatic exchange systems. SIEMENS BROS. & CO., Ltd., Caxton House, Tothill Street, Westminster, HUMPHRIES, H. E., 61, Rochester Way, and CLARK, R. I. H., 65, Humber Road, both in Blackheath, London. Sept. 24, 1934, No. 27395. Addition to 408,439. [Class 40 (iv)] A test relay which operates over two windings in series by means of its change-over contact shunts one winding to mark the outlet busy and inserts a previously shunted auxiliary relay in the driving circuit to stop the switch. Fig. 1 shows the application to a motor-driven selector controlled by a latch magnet LM, the test relay T and auxiliary relay TA being in the common control circuit CCS. A rectifier RE, in addition to preventing operation of T by metering battery, tends to prevent operation by reduced current over the test wire of an outlet associated with a busy common control circuit CCO. The latter effect may also be obtained by a lamp in series or in parallel with T. The test wires of all the outlets are normally connected to battery over a resistance YA in the control circuit CCO, and upon operation of JB subsequent to that of the line relay, the coupling relays K are brought into circuit and that of the seized outlet energizes. Typical resistance values for T, TA, K and YA are given. In Fig. 2 the test wires include rectifiers R and are connected in multiple to YA. The coupling relays K are brought into circuit by the operation of the guard relay B (not shown), and the rectifiers R prevent earth on one test wire from being extended to the other test wires. In Fig. 3, the test wires are permanently connected through the rectifiers R to YA, while the coupling relays K are simply multipled together. The relay K of a seized outlet energizes over a circuit including all the other relays K in parallel, and its release is brought about by a break contact (not shown), in series with YA. In Fig. 4, the test circuit includes the relay K shunted by a metallic filament lamp LO which assumes a higher resistance when current passes. The resistance YA is in series with a carbon filament lamp LC which assumes a lower resistance when current passes, both being shunted by a condenser QA. This arrangement prevents two test relays holding in parallel but assists in bringing about the operation of the relay K of a seized outlet. The lamp LO may serve subsequently for supervision. Fig. 5 shows the adaptation of the circuits of Fig. 1 to a double-wiper selector, the test relays TP, TS both controlling the latch magnet LM and the auxiliary relay TA and the former having preference if both the tested outlets are idle. Switching is dependent on HC which is connected up by TA, and wiperswitching is dependent on WC which energizes in series with HC when TP is up.