The 7-pin plug-in system 12 V according to ISO 1724 / ISO 3732 is the most widely used system for electrical connections between towing vehicle and trailer with 12 V on-board network. The system is primarily used for applications with average requirements. It consists of a standard connector, type N, according to ISO 1724 and an additional connector, type S, according to ISO 3732. The additional system differs from the standard system by its white housing, contact inserts and interchangeable contact arrangement.