This Recommendation covers functional requirements for a Flexible Multiplexer (FM). The FM stands for an equipment or the relevant functions able to provide time division multiplexing and demultiplexing of signals supporting a variety of user services. In addition the flexible multiplexer provides enhanced management capabilities. It is based on 64 and n  64 kbit/s services. The flexible multiplexer can be used in the access part of a digital transmission network (PDH in the case of this Recommendation).

This Recommendation mainly describes the provision of analogue and digital leased line services. Some technical solutions for the transport of PSTN and ISDN signals are also indicated. The provision of on-demand services according to Recommendations G.964 and G.965 specifying the V5 interfaces are for further study.