Martindale vt3 non contact voltage and magnetic field indicator martindale marvt3 p the martindale vt3 combines a non contact voltage detector with a magnetic field indicator suitable for detection of ac voltages in walls sockets cables circuit breakers and more with a detection range of 200v 1000v this is a handy tool for any electrician fitting comfortably into your pocket with the aid of a clip p p the vt3 is simple to use and features a red light in the tip which illuminate