A mechanical key and lock set with a rotating cylinder includes an electronic interlock which is responsive to the insertion of a mated key in the cylinder and proper rotation of the cylinder. A sensor is placed in communication with the cylinder and senses proper rotation of the cylinder to generate an activation signal. Systems controlled by the lock cannot be enabled without the generation of the activation signal. Fail safe blocking circuitry is placed in communication with the activation signal generator and in the event the actuation signal is attempted to be read in an unauthorized manner without properly rotating the cylinder, the blocking circuitry is functional to preclude reading.