The SN 4 tester is a great tool for professional electrical engineers, maintenance workers, and do-it-yourselfers. It measures and automatically differentiates between DC and AC voltages from 110 V to 400 V. It can determine the voltage polarity for DC voltage. In addition, it determines the phase conductor, tests the continuity of circuits and determines the sequence of phases in a three-phase system. It conveys all this to you with the help of LED signaling. The tips of the tester are designed to withstand high mechanical stress. The SN 4 tester will surprise you with its wide range of functions at an affordable price, so get it as soon as possible.