This British Standard specifies requirements which will permit, by means of a socket and a plug, type 12 N, inter-changeability of electrical connections between towing vehicles and towed vehicles (see figure 3).
These requirements apply to vehicles fitted with electrical equipment operating at a nominal voltage of 6 V or 12 V.
These sockets and plugs are not interchangeable with type 12 S (supplementary) sockets and plugs. (See BS AU 177.)