The Fluke Networks C9974 Voltage Detector Kit with test plug detects AC and DC voltages through a long-life carbide tip, which is protected by a plastic cap when not in use. To use the C9974 Voltage Detector, you simply place the carbide tip on the object in question, and observe the LEDs. If the Green LED illuminates, the surface being touched is free from electrical hazards. If the Red LED flashes, dangerous voltage is present.