Kewtech Mains Socket Tester with loop check, mains polarity and RCD test. The most advanced socket tester available, for front line personnel. Includes a standard socket test (checks the wiring configuration at the socket), a loop test (the standard socket test checks the presence of the earth connection, the 107, more importantly, also checks the quality), a mains polarity (check on the correct polarity coming into the building) and a 30mA RCD check. A standard socket tester does not check for the quality of the earth connection – the Kewtech 107 does. A standard socket tester cannot detect a neutral live reverse at the incoming supply – the Kewtech 107 does.