In the maximum version the trailer interface serves to amplify the direction and warning flasher lights as well as the brake lights and the rear fog lamps to the trailer. Furthermore park-boy and rear lights are switched off when trailer is connected. Another application of the switch-off operation is the use as alarm system. Is the trailer removed without permission, the horn is activated. Please take into consideration that quiescent current is higher during the monitoring (connected relay is active). Flasher lights of the trailer are breakdown monitored. Additionally the fuse to the trailer interface is monitored. Defects are indicated by the duplication of flash frequency.

For connection of the trailer interface the connections between flasher (direction switch) and rear flash lamps has to be disconnected. The connections of the direction switch are connected with IL respectivley IR, the connections to the rear flash lamps with HL respectively HR.