Abstract: The present system provides a key device which, when fitted into a key receptacle, connects a certain number of electrical circuit terminals so that certain necessary relay circuits, connected to said terminals, are energized whereby a circuit to energize a solenoid and thereby open a lock is completed through a relay tree provided that certain interrupt relays remain unenergized. If the wrong key device is used, the necessary relay circuits will not be energized and one or more of the interrupt relays may be energized whereby the lock solenoid will not be energized and an alarm may be turned on. The system further provides a power failure means which accepts a mechanical key and when the mechanical key has passed the proper tumblers, the lock solenoid will be energized.