GB1104492A - A relay circuit arrangement - Google Patents

Abstract

1,104,492. Systems including two supply sources. ASSOCIATED ELECTRICAL INDUSTRIES Ltd. 18 Jan., 1967 [10 March, 1966], No. 10619/66. Heading H2H. A system comprising two electrical equipments E1, E2 which may be first choice and standby equipments in a telephone system is provided with a selector switch S and relays A, B whereby either equipment may be selected as the first choice, the other becoming the standby equipment which takes over automatically on failure of the first choice equipment. When the positive supply voltages are connected to both equipments E1, E2 both relays A, B will tend to operate, the operative relay however being selected by the switch S. Should the equipment E1 be the desired first choice, switch AA in the selector switch is operated which places a short circuit on relay coil wB thus preventing the relay B from operating. Relay A thus operates, closing contact a1 to place a self maintaining short circuit on coil wB and closing contact a2 to complete the circuit for the selection of equipment E1. Should a failure occur in the supply to equipment E1, relay coil wA becomes de-energized thus removing the self maintaining short circuit on coil wB whereupon relay B operates and the equipment E2 brought in as standby. Selection of equipment E2 as first choice may be made by operation of switch BB in the selector switch in which case equipment E1 automatically takes over on failure of the supply to equipment E2. The relays A, B may be of the read type.