Abstract: Portable apparatus for testing the quality of a ground connection between the ground prong of a tool plug and the tool housing, and for testing the quality of insulation between the tool plug power prongs and the tool housing. The apparatus comprises an enclosure having a plug at one end adapted to be received into a conventional utility wall outlet and a receptacle at the other end for receiving a tool power plug. A pair of electrical contact plates are provided as two adjacent outside walls of the enclosure. Threshold detection circuitry carried internally of the housing is connected to the power and ground receptacles of the apparatus plug and to the contact plates. A first portion of the circuitry is effective for measuring the resistance between the ground prong of a tool plug inserted into the apparatus receptacle and a tool housing in physical contact with one of the contact plates.

Abstract: A device for testing electrical continuity at an industrial or household grounded A/C power outlet which is connected to an A/C line voltage through a ground fault circuit breaker. The device includes a housing having at one end thereof an A/C hot, an A/C neutral and a ground prong, and at the other end three lamps electrically connected between corresponding pairs of prongs to provide an indication of the presence or absence of an A/C voltage between the prong pairs when the prongs are received in plug-in connection into the outlet to be tested. The device further includes a momentary switch electrically connected between the A/C hot prong and the ground prong, and which, when activated, provides an overload current leakage path from the A/C line to ground so that the device may be used to check both the electrical continuity at the outlet and the operability of the ground fault circuit breaker in a single step.