The R5500 instrument features a Circuit Breaker finder, a Circuit Tester and a GfCI Receptacle Tester. Quickly and easily identify the correct circuit breaker protecting a specific electrical circuit without service interruption. Simply plug the transmitter into a receptacle and scan breaker box to identify the circuit. Detects 5 3-wire receptacle wiring faults. Built-in GFCI receptacle check function. Adjustable sensitivity wheel quickly identifies breaker. Audible (buzzer) and visual (LED) indicators assist in identification. 4" (h) x 2. 2" (w) x 1. 2" (d). Weighs 3. 88oz. frequency range of 47 to 63Hz. Receiver is powered by a 9V battery (included). 3-in-1 tester locates breakers, tests receptacles and GFCI circuits.