You can check if the following devices are energized: ・Outlet (two locations simultaneously, exposed type also possible) ・Ceiling fixture (round and square types) ・Construction-omitted section ・Lamp receptacle → Lights blue when current is flowing correctly → Lights red when current is flowing, but the wiring is incorrect (for example, if the black wire is connected to the receptacle screw terminal) (In the photo, the ground and non-ground wires are connected in reverse to make it light red) Cannot check 200V circuits, ground wires, construction errors such as crimping failures, pilot lamps, or the illumination of firefly switches. ～Wiring check for circuits using substitute terminal blocks～ For circuits using a time switch substitute terminal block, etc., check using a separate jumper wire. A paper with instructions on how to check and a jumper wire are also included. ～Set Contents～ Battery box x 1 Outlet checker x 2 Ceiling fixture checker x 1 Construction-omitted section checker x 1 Lamp receptacle checker x 1 ～Precautions for Use～ Power supply: 2 AA batteries (not included)