Touch the tip to a terminal strip, outlet, or supply cord. When the tip glows red and the unit beeps, you know there's voltage present. Electricians, maintenance, service, safety personnel, and homeowners can quickly test for energized circuits. This unit is very lightly used. A new one is $45+, for example on Amazon. This is $25 including delivery in the West Shore, Saanich, View Royal, Esquimalt, or Victoria. Thanks for looking.