While other receptacle testing devices will verify correct wiring and the existence of some type of ground, only Stop Shock Hazardous Ground Circuit Analyzer will test and verify a safe low impedance ground thereby insuring the safety of the AC circuit wall outlet, multiple outlet strip or extension cord being used. Only Stop Shock can help you avoid personal injury and costly damage to computers, home entertainment equipment & electrical appliances by instantly detecting high-impedence hazardous grounds and faulty wiring conditions.