Ac Plug Circuit Checker
To check the wiring of 110VAC power sockets.
AC plug circuit checker.
Plug this device into a 110 VAC socket. It will indicate either that the socket is wired properly or, if not,exactly what wiring error was made. In fact, several wiring errors were found in the Physics Department wiring using this gizzit when we first got it. This is the device that the county electrical inspector uses for the home wiring inspection after the wiring has been installed by the do-it-yourselfer.
Thomas James Higgins, Evolution of the Three-Phase 60-Cycle Alternating-Current System, AJP 13, 32-36 (1945).