Salisbury's Self-Testing Voltage Detectors allow testing to be continuous and automatic. An intermittent flash and beep confirms the detector is functioning properly. Self-Testing Voltage Detectors are used to verify live or de-energized conductors. These testers may be used with rubber insulating gloves or hot sticks using the splined universal end fitting. Each tester has a 4.5 volt transistor amplifier with an audio/visual indicator. It is recommended that the tester be moved closer to conductor until warning is indicated, or it touches conductor, apparatus, or elbow test point. Test the unit on a nearby energized conductor. To get verification of proper operation set tester on lowest setting. Each tester includes three alkaline "C" batteries.