Indicates faults in the car or trailer lighting wiring circuits. Plug and play, no cutting or splicing required CE EN61000, RoHS EN62321 certified, using high-quality ABS + copper material, durable matte black housing Simply plug the lighting and cable tester into the socket or plug to be tested, press the test button, and the LED display can provide clear diagnostic information. 12V electric trailer socket tester, one end of the trailer is connected to the vehicle's 7-pin plug and socket, normal European standards commonly used in cars, caravans, RVs and other vehicles. You need a 9V square battery to activate the tester, otherwise it will not work (not included) Specifications: Material: Plastic and Copper Voltage: DC 12V Package Content: 1 x tester Tips: The plugs in the box can be inserted directly into the 7-pin plug or socket and check the continuity of all lighting circuits How to test the connection of a trailer (can also be a caravan, bike, van or other commercial vehicle)? 1. Connect the tester with a plug or socket 2. Press the yellow button on the side of the tester 3. With good wiring, all LEDs will light up