1Trailer tester for 7-pin plug and socket connection. 2Used to test whether the trailer power supply wiring is normal. 3With 6 LED indicators for easy observation. 4Clearly show any faults in your wiring on your car or trailer. 5Lightweight and portable, easy to operate, worthy of your trust.1 xSocket Connection TesterCondition: 100% New_x000D_Item Type: Socket Connection Tester_x000D_Color: Shown as Picture_x000D_Material: ABS+ Copper_x000D_How to test the connection of a Trailer (can also be a caravan or bicycle carrier)_x000D_1. Put the plug in the connection of the tester._x000D_2. Press the yellow button on the side of the tester._x000D_3. If the wiring is good, all the LEDs light up. the function of each LED is (acc iso 1724):_x000D_A. Left Hand Indicator (yellow)_x000D_B. Fog Light or 12v (blue)_x000D_C. Mass (white)_x000D_D. Right Hand Indicator (for Green)_x000D_E. Right Rear Light (brown)_x000D_F. Left Brake Light (red)_x000D_Left Rear Light (black) 1Trailer tester for 7-pin plug and socket connection. 2Used to test whether the trailer power supply wiring is normal. 3With 6 LED indicators for easy observation. 4Clearly show any faults in your wiring on your car or trailer. 5Lightweight and portable, easy to operate, worthy of your trust.1 xSocket Connection Tester