In two parts specifies design, construction and performance requirements and configurations and dimensions for three types of 7-pin connectors for making detachable connections between vehicles (both private and commercial) and trailers fitted with 6 V, 12 V, and 24 V systems. Future 12-pin connectors are covered only to the extent that functions are allocated to pin numbers, and compatibility with the same type of 7-pin connector is specified. Based on ISO 4091, with some changes.