Sperry makes the job of locating electrical circuits (AC circuits of 110-125 volts) quick and easy. Turning off the correct breaker is critical when considering work on an electrical circuit and can take an excessive amount of time using "trial and error" until you hit the right one. This Circuit Breaker Finder features a sending unit that you plug into a receptacle in the room where you want to work and a receiving unit which you use to test the breakers to correctly identify the right breaker every time. The receiver features both a visual flashing light and an audible beeping to alert you when the correct breaker is identified. The package includes a user manual and a 9 volt battery required for the receiver unit.