Plug and test with ease.  This unit is used to troubleshoot 120V AC grounded outlets.  Designed to work with typical 3-wire NEMA 120 volt receptacles.  Light sequence gives a visual indication of correct/incorrect wiring.  Ergonomically designed to fit comfortably in the hand for hours of testing.  The GT-10GFI works with GFI outlets and confirms that the ground fault outlet is working properly. Independently tested to UL’s protocol 1436.  Manufactured by Greenlee.