Fog Lamp Sensor

For several years now, a rear fog lamp has been mandatory for trailers and caravans in order to improve visibility under foggy conditions.
When this fog lamp is switched on, the fog lamp of the pulling vehicle must be switched off to avoid irritating reflections. For this purpose, a mechanical switch is now built into the 13-way female connector in order to switch off the fog lamp of the pulling vehicle and switch on the fog lamp of the trailer or caravan.
For anyone who uses a 7-way connector, this switching can also be implemented electronically with the aid of the circuit discussed here.