Abstract: A DTMF encoder at a central office is connected to a spare pair of a feeder cable for remotely controlling with a 5-digit number a series of relay coil matrices where the coils perform latch and release functions for 50 latching relays in each matrix. Two of the digits select the matrix and two other digits select the relay coil to be energized. The fifth digit selects the crossconnect box or pedestal from a plurality of the same. The 50 relays are connected in pairs to serve 25 incoming pairs, each pair of relays being arranged to selectively connect its associated incoming pair to any one of three corresponding outgoing pairs or terminals. Energizing current is supplied to a selected coil only upon receipt of the last of the five digits and only for a brief interval. Power for the remote apparatus is supplied from the central office via a phantom circuit over the same spare pair.

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.