1Practical Function: This adapter is a lighting and cable tester for trailers and towing vehicles. Our test device guarantees the fastest and easiest search for cable line defects on trailers and on towing vehicles. 2Easy to Operate: Defective cable colors are indicated by the device via LEDs. All 13 pin sockets and plugs can be checked. To do this, you simply have to insert the tester into the socket to be tested, press the test button and a clear diagnosis is made via the LED display. 3Durable Construction: Made of high strength Abs plastic and copper, which is impact resistant, wear proof, anti aging, and has long service life. 4Excellent Performance: Using brass as conductor, with good electrical conductivity, ensuring more stable function and high practicality. 5Battery Powered: Due to the internal battery supply, no external power source is necessary. Trailers tester do not have to be connected to the vehicle either.