Abstract: A port detection and protection circuit utilizes a voltage detection circuits to output a detection signal according to a voltage difference between the tip signal and the ring signal and utilizes a ring detection circuit to output another detection signal according to a voltage difference between a Subscriber Line Interface Circuit (SLIC) tip signal and a SLIC ring signal signaling an incoming call. In addition, the port detection and protection circuit utilizes at least one logic component to output logic signals according to the detection signals. The port detection and protection circuit further switches a loop of a tip wire, a ring wire and the SLIC on or/and off based on logic signals, and issues an alarm according to the logic signals.

Abstract: A port detection and protection circuit utilizes a voltage detection circuits to output a detection signal according to a voltage difference between the tip signal and the ring signal and utilizes a ring detection circuit to output another detection signal according to a voltage difference between a Subscriber Line Interface Circuit (SLIC) tip signal and a SLIC ring signal signaling an incoming call. In addition, the port detection and protection circuit utilizes at least one logic component to output logic signals according to the detection signals. The port detection and protection circuit further switches a loop of a tip wire, a ring wire and the SLIC on or/and off based on logic signals, and issues an alarm according to the logic signals.