Abstract: Apparatus for use with a source of A.C. electrical power and for monitoring both the ground and polarity integrity thereof. The apparatus, which is configured to receive a polarized electrical plug, makes connection with the normally hot, neutral and ground outputs of the source of electrical power and includes a normally open indicating circuit connected to the normally hot power output. Insertion of the polarized electrical plug completes the circuit to the normally ground output and, if the ground line is intact and the polarity proper, the indicating circuit provides an indication of this fact. If, on the other hand, either the ground line is open or the polarity is improper, the indicating circuit will indicate that the source is unsafe to use. Means are also disclosed for correcting an improperly polarized service receptacle and for providing safety indications directly in combination with an electrical tool or the like.

Abstract: An alarm circuit for deterring the theft of electrical devices of the type normally plugged into an electrical power receptacle by providing an alarm signal whenever the electrical plug associated with the electrical device has been removed from the receptacle. The alarm circuit comprises an electrical power receptacle having hot, neutral and ground female contacts adapted to receive an electrical plug having corresponding electrical contacts, the receptacle also including a switch for connecting the neutral conductor to the ground conductor upon insertion of at least one of the male contacts associated with the plug. An indicating circuit in association with the receptacle provides an alarm signal when the electrical plug is removed from the receptacle.