Tests Ground Fault Breakers By Overloading Circuit And Tripping GFCI. Plug Tester Into Any Ground Fault Receptacle (110-125 Volt AC) And Press Black Button To Overload Circuit. Tests For Seven Conditions; Ground Fault Interruption, Open Ground, Open Neutral, Open Hot, Hot/Ground Reverse, Hot/Neutral Reverse And Correct Wiring. Yellow And Red Lights Provide Indication Of Circuit Status Or Specify Which Wire Is Defective. Carded.