It is a Non-contact tester that I use to easily Detect Voltage in Cables Cords Circuit Breakers Lighting Fixtures Switches Outlets and Wires. It is a Non-contact tester that I use to easily Detect Voltage in Cables Cords Circuit Breakers Lighting Fixtures Switches Outlets and Wires. This popular tester is also used by most inspectors to test for power and check the polarity of circuit wiring. Source: https://www.artikelschreiber.com/en/.