For use on 110-125 VAC receptacles. To test, simply plug into receptacle and observe the light pattern. Push the yellow button to test operation of ground fault receptacle. Instructions: (1) Test the Plug-Bug 2 on a known good receptacle before using on other receptacles. (2) Insert Plug-Bug 2 into receptacle to be tested and observe lights. (3) If testing a GFCI protected receptacle, insert Plug-Bug 2 into receptacle and observe lights. AC power must be present in order to test a GFCI. The receptacle must be wired correctly before proceeding (see Chart). If no lights come on, AC power is not present or the receptacle is improperly wired. If lights indicate proper wiring, press the Plug-Bug 2"s TEST button. If the GFCI is working, the Plug-Bug 2"s indicator lights will turn off. The TEST LED may flash briefly. If the indicator lights do not turn off, and the TEST LED remains lit, the GFCI is not working, or the circuit being tested is not GFCI protected. (Do not press the TEST button for more than 6 seconds). To re-apply power to the GFCI protected circuit, press the RESET button located on the receptacle or the GFCI circuit breaker.