GTC cordless circuit tester is a computer safe, all solid state electronics circuit tester. This high-impedance circuit tester is safe to use around automotive computers, electronics, ecm's, sensors and air bags. Rugged, built to last and simple to use, it requires no wire or clip connector to ground. The Cordless Circuit Tester's light and sound indicators allow users to check for power in less time that it takes to set-up a regular test light and find a suitable ground. Designed for use in automobiles, trucks, tractors, trailers, RV's, motorcycles, boats and any DC powered circuit from 3 to 28 volts.