The Klein Tools ET310 Circuit Breaker Finder with Integrated GFCI Outlet Tester is a digital circuit breaker finder used to locate the correct circuit breaker in a panel to which an electrical outlet or fixture is connected. The Transmitter is connected to the electrical outlet or fixture in the circuit while the receiver is used to scan the breakers in the circuit panel. The Transmitter also features a GFCI outlet tester. For more than 160 years, Klein Tools has manufactured premium-quality, professional-grade hand tools that deliver the performance, durability and precision needed to get the job done right. Our family of engineers, workers and craftsman continue to put six generations of expertise into every tool we create by using only the highest quality materials, superior workmanship, and keeping manufacturing as close to home as we can. Klein isn't just the name of our company, it's also our family name. And since we're an American company that's family-owned and family-run, you know you can count on us to be here tomorrow. Klein Tools doesn't just make great products, we make great products that stand up to the demands of the professionals who use them every day ... Since 1857.