Upon connecting the instrument to the vehicle’s battery, you can detect if a circuit is Positive, Negative or Open. You can do this by probing it and observing the RED or GREEN LED. To quickly activate electric components, press the power switch to activate. It is short circuit protected. Continuity of switches, relays, diodes, fuses and wires are easily tested by connecting them between the auxiliary ground lead and the probe tip. To confirm continuity, observe the GREEN LED. Check fuses and test for short circuits. Find faulty ground connections instantly. The 6 m. lead will reach from bumper to bumper and it has the option to connect an additional 6 m. extension cable to make it reach up to 12 m. Great for trucks, trailers, and motorhomes.