The new Technologies that nowadays are applied in the vehicles (Check Control, Can Bus Data..) make necessary the installation of specific wiring kits developed for each vehicle. These kits incorporate: original connectors, modules that interpret orders, vehicle fog light disconnection etc. Most specific wiring kits disconnect the PDC (parking distance control).  
                                                                                       
Depending on the electronic system of the vehicle, the wires for the trailer or caravan are connected through original connectors or direct to the CAN BUS line of the vehicle.

See FAQ section

Characteristics:
The module is programmed with the CAN BUS protocol specify by the vehicle manufacturer. Most of the times is an OEM module.

Advantages:
The fitting instructions are precise and specific for each vehicle
The fitting times are specify on the catalogue.
The CAN BUS technology has helped to reduce the quantity of wires of the car.