COMMUNICATION LINE SWITCHING DEVICE

PROBLEM TO BE SOLVED: To realize a switching device that disconnects a subscriber's equipment and forms a continuity path for a measurement signal suitable for locating a fault location through the use of a remote control self-hold relay even on the occurrence of an earth fault or a fault contact. SOLUTION: When a negative pulse with a voltage in excess of a voltage of a constant voltage diode of a 1st changeover control circuit 1 is applied between a terminal L1 and an earth E as a 1st control signal, a relay RL1 is activated, which self-holds. A 1st continuity means 3 is connected, subscriber terminals T1, T2 are open and a 1st switching state is realized. The switching state is recovered by applying a normal operating voltage between terminals L1, L2. When a positive pulse with a voltage in excess a constant voltage of a constant voltage diode of a 2nd switching control circuit is applied between either of the terminals L1, L2 and the earth E as a 2nd control voltage, a relay RL2 is activated, which self-holds. A 2nd continuity means 6 is connected, the subscriber terminals T1, T2 are open and a 2nd switching state is realized. A 2nd return control circuit 5 is operated after a prescribed time and the 2nd switching state is recovered through the application of a normal operating voltage.