It is used to check the 13-pin electrical trailer sockets that are fitted to vehicles with tow-bars. If the sockets are faulty, then secondary lights fitted to the trailer or caravan may not work correctly. BTT-111 checks the output from each pin on the socket and determines its operation.

With the majority of caravans and trailers still using conventional 7-pin sockets, BTT-111 is supplied as standard with an adapter plug to ensure complete coverage of the market. It has a membrane keypad with integrated LED indicators to signify correct output when the vehicle controls are operated, and a TEST button is also included in order to illuminate the LEDs and check the tool is operating correctly prior to testing the vehicle.

BTT-111 is fitted with an internal battery enabling the TEST feature to operate without the presence of power (not available from 7-pin sockets). When using the TEST feature on a 13-pin socket, the battery is automatically bypassed and power is taken directly from the vehicle, thus increasing battery life.