According to ECE R48, the rear fog light (RFL) of the towing vehicle may be deactivated when towing a trailer. When installing carriers (for example for bicycles) with lighting systems, the RFL has to be cut off to lessen the glare.

The rear fog light cut-off cuts off the vehicle's RFL. It is independent on whether the trailer has RFL or not. The rear fog light changeover changes the load of the RFL from towing vehicle to trailer.

The automatic switching between on and off of the towing vehicle's RFL can be controlled as follows:

• by a mechanical cut-off contact in the socket
• by a micro switch in the socket
• by an additional rear fog light cut-off relay
• by the ERICH JAEGER trailer control device with trailer identification