Purpose] This socket tester can check the electrical connection of the socket whether correct. It is a good tool which is used to ensure electrical safety at home. The tester can be used for electrical maintenance in schools, laboratories, factories and other social areas. It is ideal for office outlet testing, power strip testing and wall socket testing. Compact size and light weight, you can store it in tool case and your bag easily, convenient to carry around. [Easy to use] Detect the neutral line, connect the wires and ground wire correctly, and indicate which line lacks the bright light mode. The lamp holder icon is labeled on the surface of the socket tester, easy to operate.