Sperry Instruments CS550A Electrical Circuit Breaker Finder, AC Circuits and Fuses, 80-140V AC, 50-60Hz QUICKLY AND EASILY: identifies correct circuit breaker or fuse protecting a specific electrical circuit SAFE FOR USE NEAR: Sensitive electronic equipment and no need to interrupt power when using INCLUDES: A plug style transmitter and an auto sensing receiver AUDIBLE ALERT AND BRIGHT LED: Visual indication on both transmitter and receiver DESIGNED FOR: Operation at 120V AC, 50-60Hz - UL Listed