This document applies to distributor valves and distributor-isolating devices. The distributor valves contained in this document are of graduable release type. Direct release types are not included. Functionally they are regarded as not containing relay valves of any type, even if the relay valves are physically an integral part of the distributor valves. This document applies to both distributor-isolating devices mounted separate from the distributor valve and distributor-isolating devices integral with the distributor valve. This document specifies the requirements for the design, testing and quality assurance of distributor valves and distributor-isolating devices. The distributor valve and distributor-isolating device are intended to be part of a brake system mounted in a vehicle with maximum length of 31 m and maximum brake pipe volume of 25 l taking into consideration brake pipe inner diameters between 25 mm and 32 mm.