The Lisle Digital Circuit Tester, No. 28830, has a digital LCD display that accurately shows DC voltage. With an operating range of 3V to 49V DC, the tester works on most vehicle electrical systems. Offering 360-degree visibility of polarity, the tester's red light indicates positive polarity, green indicates negative polarity. A 12' coil cord and heavy duty alligator clamp for secure connections are included, and the probe is insulated to prevent the possibility of shorting the side of the probe to other components. The device is computer safe and will not damage sensitive electronic components. It is not for use on air bags.