This standard specifies an identification mark on the interface of various components of the air brake system of automobiles and trailers (including the pneumatic components in the air cap fluid brake system). This standard applies to automobiles and trailers, and can also be used for schematic diagrams of braking systems.
GB/T 5921-2015 history
2015GB/T 5921-2015 Motor vehicles and towed vehicles.Air braking systems.Identification of connections on units
1986GB/T 5921-1986 Motor vehicles and towed vehicles--Air braking systems--Identification of connections on units