System using the telephone network to control locks at a number of remote locations

A number of remotely located locked devices (26 and 27) are selectively operated by sending signals from a central supervisory location (28) through the telephone network (27) to a telephone set 32 and a converter (44) installed at each remote location. Initiating call signals from a remote telephone set are automatically generated and routed through the telephone network to a supervisory telephone set equipped with a standard 0-9 digit dial plus a special pushbutton (34) for generating a special signal. Receipt of the special signal at a calling remote station disconnects the remote telephone set and conditions a stepping circuit (74-86) and a sequence circuit (81-82) for subsequent operation upon receipt (88-104) of a predetermined sequence of 0-9 digit signals. Upon receipt of the predetermined sequence of signals within a first set time period, the stepping circuits and the sequence circuits are operated to generate (111) a signal that releases the locked device for a second set time period.