Recommendation Q.71 is the Stage 2 definition for point-to-point circuit mode switched bearer services. These services include speech, 3.1 kHz audio, multi-use 7 kHz, unrestricted and n ´ 64 kbit/s information transfers as well as broadband connection-oriented bearer services.
Stage 2 identifies the functional capabilities and information flows needed to support the service description. It provides information on the functions in ISDN entities and the information flows between the entities which are required to provide call set-up and call release procedures. This includes the description of the interfaces to the various supplementary services and the interface to private networks.