Amprobe ST-102B Socket Tester with GFCI Tests standard & GFCI sockets/outlets/receptacles for proper wiring (110-125V AC) Verify proper wiring of GFCI (ground fault circuit interrupter) and standard US and Canadianwall outlets with a simple push of a button Detect five different wiring faults [open ground, open neutral, open hot, hot/ground reverse, and hot/neutral reverse] UL and CSA listed for safety