The Extech 480400 phase sequence tester has a nominal range of 40 to 600 volts for testing the phase direction of three-phase sources over a frequency range of 15 to 400 Hz. The multi-line LC display shows the phase direction (clockwise or counterclockwise) and whether the individual phases are live. No battery required. The scope of delivery includes cables, three large, color-coded crocodile clips and a carrying case.