a combination mechanical and electronic lock system for use in cuffs and various other locking applications is disclosed . in the preferred embodiment , the lock is configured to receive a matching key that transmits a code that disengages the electronic lock from the mechanical lock so that the mechanical lock can be manually opened by the user . when implemented in a handcuff , for example , the mechanical lock includes a single lock mechanism and a double lock mechanism ; and at least one electronic lock configured to selectively unlock at least a portion of the mechanical lock upon receipt of the proper digital code from the cuff key . the power needed to operate the electronic lock , preferably a solenoid or other actuator , is received directly or indirectly from the cuff key so that the cuff need not possess a battery .