The Hand Held power supply is designed to provide a single phase known voltage source for the test and verification of a voltage detector. It is recommended to use this tool before and after each use of the meter to verify function of the meter to prevent false indications in the event of a tool malfunction. It is specifically designed for use on non-wired voltage detectors. The supply provides an approximately 800 volt output, varying slightly in relation to the actual voltage of the 9V battery that supplies the unit. The readings the meter will give will also slightly vary depending on the unit being tested and the position of all the components.