The Extech CB20 lets you locate the correct circuit breaker or fuse without turning off the power, which employs automatic sensitivity to quickly and accurately pinpoint the correct 90-Volt to 120 VAC circuit breaker or fuse. The CB20 is ideal for a range of applications, including locating branch circuit breakers without causing accidental power shutoffs, confirming proper wiring during electrical installation or repair, and testing receptacle ground fault operation.