Calling subscriber party line identification circuit

Claim 1

An identification circuit for identifying individual parties in a party line system and for enabling the supply of party identification to a central identification system, wherein the improvement comprises: means for receiving an identification demand signal; a tone generator for supplying an AC tone; means responsive to an identification demand signal to connect AC tone to a first line of a party line; a first subscriber connectable directly between the first line and a second line of the party line; a second subscriber connectable in series with an attenuator between the first and second lines of the party line; a control circuit connected by a first terminal to the second line, and by a second terminal to receive the identification demand signal; said control circuit responding to the presence of AC tone on the first terminal and an identification demand signal on the second terminal to operate means for supplying an indication that the first party is calling; said control circuit responding to the absence of AC tone on the first terminal simultaneously with the presence of an identification demand signal on the second terminal to operate means for supplying an indication that the second party is calling; the control circuit including a one-shot trigger circuit settable by the identification demand signal to provide a time delay after which it provides a delayed pulse; a flip-flop circuit providing an output signal in response to the delayed pulse from said trigger circuit; and said output signal operating he means indicating that the second party is calling.