Stop Shock Hazardous Ground Tester & Circuit Analyzer Model HGT 120 A Green light indicates no hazardous wiring conditions exist. - Outlet safe to use! Red light flashing shows hazardous faulty ground wire. - Do not use outlet! Voltage Range: 80-140 Vac max. to ground Frequency: 50/60 Hz Dimensions: 3.3"H x 2.6"W x 1.1"D (83 x 67 x 28mm)