Review on 🔌 Sperry Instruments VD7504GFI: DualCheck Non-Contact Voltage Detector + GFCI Outlet Circuit Analyzer with Visual & Audible Indicators, 50-1000V AC, 250 lb. Crush Rating by Alexander Scharon

Crazy "button" battery is NOT included and there is no battery polarity indicator on the unit so you'll have to guess. device to work. Other brands stay on for a while when you turn them on, then turn off automatically after a minute or two. Not as sensitive as more popular brands (can't read if you hold it to the face of an active switch or outlet). I ran a parallel test. So it works, but you need a custom battery and it doesn't work as well as the others for a number of reasons.