TELEPHONE METERING INTERFACE WITH REVERSE SIGNAL SENSOR

摘要

A sensing circuit is placed in the tip line of a subscriber's loop to sense, selectively, the placement of an outgoing, local call. The circuit includes a first LED for energizing a metering circuit upon detection of a billable call, and a second LED for latching the metering circuit in its energized condition within a predetermined interval after the billable call is detected. The metering circuit is automatically deenergized when the called party goes on-hook. A balancing circuit is included in the ring line of the equipment to balance the impedance created in the tip line by the sensing circuit; and the metering circuit can be designed selectively to produce a one-shot metering pulse for each billable call, or to produce a continuous signal for the duration of the call.