The present document specifies the stage three of the diversion supplementary services for the pan-European Integrated
Services Digital Network (ISDN) as provided by European public telecommunications operators at the T reference
point or coincident S and T reference point (as defined in ITU-T Recommendation I.411 [9]) by means of the Digital
Subscriber Signalling System No. one (DSS1). Stage three identifies the protocol procedures and switching functions
needed to support a telecommunication service (see ITU-T Recommendation I.130 [4]).
In addition, the present document specifies the protocol requirements at the T reference point where the service is
provided to the user via an intermediate private ISDN.
The present document does not specify the additional protocol requirements where the service is provided to the user
via a telecommunications network that is not an ISDN.
The diversion supplementary services comprise the following services:
- Call Forwarding Unconditional (CFU) supplementary service;
- Call Forwarding Busy (CFB) supplementary service;
- Call Forwarding No Reply (CFNR) supplementary service;
- Selective Call Forwarding Unconditional (SCFU) supplementary service;
- Selective Call Forwarding Busy (SCFB) supplementary service;
- Selective Call Forwarding No Reply (SCFNR) supplementary service;
- Call Deflection (CD) supplementary service.
The CFU supplementary service enables a served user to have the network redirect to another user calls which are
addressed to the served users ISDN number. The CFU supplementary service may operate on all calls, or just those
associated with specified basic services. The served users ability to originate calls is unaffected by the CFU
supplementary service. After the CFU supplementary service has been activated, calls are forwarded independent of the
status of the served user.
The CFB supplementary service enables a served user to have the networ (...abbreviated)