Patent US 3,939,679

Normally disabled electrical and mechanical devices are caused to be enabled to operate by remote control signals having predetermined distinctive characteristics, such signals originating from enabling control equipment transported by an authorized person or persons. Receiving equipment providing output enabling signals only in response to received signals having the predetermined distinctive characteristics is preferably made integral with the mechanical or electrical devices involved and is coupled through appropriate electronic or electromechanical devices to the disabling means in the mechanical or electrical devices to be enabled.