This standard specifies an identification method for the interface on each component of the air brake system (including the pneumatic components in the air-hydraulic integrated brake system). This standard applies to automobiles and trailers, and can also be used for schematic diagrams of braking systems.
GB/T 5921-1986 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