Pulse receiver circuit providing longitudinal balance

摘要

A pulse receiver for connection in a telephone circuit including two coils connected between a voltage potential and ground further including an external impedance that is alternately connected between the coils. The pulse receiver includes a first impedance connected in series with the first coil and a second impedance equivalent to the first impedance connected in series with the second coil and an input circuit connected across the first impedance for detecting the connection of the external impedance of the telephone circuit. Switching circuitry is provided that is connected to the input circuitry and alters a first output node pair from a normally closed state to an open state and alters a second output pair from a normally open state to a closed state in response to a signal received from the input circuitry indicative of the detection of the external impedance connection.