Identifier circuit for identifying party line subscribers

Abstract

An identifier circuit for connection between a telephone system party line and a party line subscriber to permit identification of a calling party line subscriber with automatic number identifying equipment at a central office. The identifier circuit includes a pair of terminals adapted to be selectively connected to ground in accordance with identification of a particular party line subscriber, a pair of normally nonconductive test transistors each connected between one of the terminals and one of the leads of the party line, a pair of control transistors responsive to voltage on the party line to maintain the test transistors nonconductive and responsive to removal of the party line voltage to permit the test transistors to conduct, and a pair of capacitors charged when a calling subscriber goes off hook and discharged to maintain the test transistors conductive for a predetermined time during which testing of the party line to identify the calling subscriber can be accomplished with automatic number identifying equipment at the central office.