Remotely actuable line disconnect device

Abstract

A disconnecting device is inserted in a two-wire communication loop near the far end thereof. The device contains a latching winding of a latching relay which winding is inserted in series with one side of the loop. The winding controls two normally closed contact pairs, one pair being inserted in series with each side of the loop to disconnect a far end telephone or the like when the winding is energized. A shunt diode and capacitor prevent activation of the latching winding by normal battery and signal current. Reverse polarity voltage of greater value than normal battery will activate the latching winding and effect far end disconnection. A reset winding of the relay is connected in series with a diac, a diode, a time constant resistor and a normally open pair of contacts of the latching relay, across the loop. Each of the normally closed contact pairs is shunted by a resistor to permit current flow past the contacts when open. A capacitor storage and timing circuit is connected with the reset winding of the relay to accumulate sufficient voltage when normal battery polarity and potential is restored to cause the diac to conduct and the relay to reset. The impedances are related so that a disconnection cannot be achieved when the telephone is in the ON-HOOK mode and there is no fault in the loop. Reconnection cannot occur while the telephone is OFF-HOOK.