Shop 30 Amp RV Surge Protector Circuit Tester 30 amp 1050 Joules Surge Protector with LED Indicator Light ETL Listed Nema TT-30P TT-30R Power Analyzer for RV Camper Trailer Van, support 2 Years Warranty with high quality. Together with the diagnostic chart provides LED indication guide for the following wiring condition: Power ON/Correct Wiring, NO Power/Open Hot, Open Ground, Reverse polarity, Open Neutral, Hot/Ground Reverse, Hot/Neutral Reversed with Neutral Open.