Lisle 28830 Digital Circuit Tester (3-48V) Operating range of 3-49 volts DC to work on most vehicle electrical systems Two LEDs provide 360 Degree visibility of polarity The red light indicates positive polarity, green indicates negative polarity Long, 12ft coil cord and heavy-duty alligator clamp for secure connections The probe is insulated to prevent the possibility of shorting the side of the probe to other components Computer safe