Abstract: A lock-out plug is provided for preventing unauthorized use of a telephone by preventing connection thereof to an operative telephone jack. The lock-out plug comprises a compact plug fitting having a size and shape to fit snugly into an open receptacle of a standard modular type telephone outlet jack. An angularly set threaded bore is formed within the plug fitting such that a forward end of the bore is disposed within the telephone receptacle and a rearward end of the bore is exposed to the exterior of the receptacle when the plug fitting is seated therein. A set screw is received within the bore and includes a forward end locking tip for binding engagement with a side wall of the telephone jack to lock the plug fitting in place and thereby prevent unauthorized connection of a telephone to the jack. The head of the set screw is accessible from the exterior of the jack preferably by engagement with a specialized tool to advance or retract the locking tip relative to the jack side wall.

Abstract: An electrical receptacle of the three contact type, one of which receives the standard, normally non-current-carrying, system ground pin of a corresponding cap.A set screw is advanced into a threaded bore in the plastic body material of the receptacle to make contact with the aforementioned ground pin. The bore may be from the receptacle front or from behind the face plate, in either case preventing the casual or surreptitious removal of the cap and cord and the associated equipment.