Telephone line interface circuit

Abstract From the Canadian patent

Abstract of the Disclosure A telephone line circuit transformer couples tip and ring leads of a telephone line to a telephone facility. Tip and ring transformer windings are connected in series with the respective tip and ring leads, tip and rings feed resistors and terminals of a battery power source for supplying energizing current to the telephone line. A capacitor is connected between a junction of the tip winding and the tip feed resistor and a junction of the ring winding and the ring feed resistor. A compensating circuit is connected to drive a compensating winding in current opposing relationship with respect to differential alternating current signals in the tip and ring windings …