Our special Pro Glo® SJTW (300V) jackets offer high visibility for safety underfoot and extra flexibility in cold weather. Each male plug has a built in amber neon light which indicates that there is power in the cords and outlet.? In addition, our Continuous Ground Monitoring (CGM) feature indicate there is a continuity in the ground wire throughout the extension cord. If the green neon light inside our clear molded connector is not lit, there has been a loss of ground continuity.