General Technologies Corp GTC CT8002 Cordless Circuit Tester Professional cordless computer safe circuit tester constructed in rugged stainless steel requires no ground wire or clip and a safety V-groove accessory is provided for piercing and carrying. Negligible current draw ( 20 micro-amps) is 10,000 times less than regular lamp type testers and is completely safe when working around sensitive electronic control modules and sensors. Operates between 3 and 28 Volt DC in battery powered systems, providing visual (LED), audio (sound) and tactile (vibration) feedback when a positive voltage is detected. Solid state high impedance electronic circuitry Operates on a single AA alkaline battery, which is included with the unit.