The Klein Tools RT390 is a Circuit Analyzer that tests the wiring conditions at an electrical outlet, displays AC line voltage, inspects AFCI and GFCI devices with time to trip device, and performs voltage drop tests at 12A, 15A and 20A current loads. Results are easy to understand with large, color LCD. The tester is designed for use with North American 120V AC 3-wire electrical outlets. 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.