Voltbeat technology and continuous self-test - so you always know it is working Upon detection, tip glows and beeper sounds CAT IV 1000 V for added protection Range 90-volt to 1000-volt 20-volt to 90-volt AC control circuit model also available Simply touch the tip to a terminal strip, outlet or cord. When the tip glows red, and the unit beeps, you know there's voltage in the line. Electricians, maintenance, service, safety personnel can quickly test for energized circuits and defective grounds on the factory floor, in the shop. Continually tests its battery and its circuit integrity with a periodic double flash visual indication using fluke voltbeat technology. It comes with a two year warranty. It detects line voltage from 90vac - 600vac (1AC-AI-II).