Instructions are very limited, but its use should be intuitive for anyone attempting to use it along with common sense precautions when working with power. It will verify the voltages of a PC ATX type power supply. Plug the power supply's system board connector into the device and then plug in the line cord and observe the lights. To test the individual device power connectors, the power supply must be plugged in as above along with the individual device connnector to be tested. Therefor it is possible to test each connector in a "bench test" mode, but not on a live machine.