scope:

The present document specifies the stage three of the supplementary service interactions 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 [32]) by means of the Digital Subscriber Signalling System No. one (DSS1) protocol. Stage three identifies the protocol procedures and switching functions needed to support a telecommunication service (see ITU-T Recommendation I.130 [29]).

The present document specifies the interactions between the Advice Of Charge (AOC), Completion of Calls to Busy Subscriber (CCBS), Completion of Calls on No Reply (CCNR), Call Deflection (CD), Call Forwarding Busy (CFB), Call Forwarding No Reply (CFNR), Call Forwarding Unconditional (CFU), Calling Line Identification Presentation (CLIP), Calling Line Identification Restriction (CLIR), COnnected Line identification Presentation (COLP), COnnected Line identification Restriction (COLR), CONFerence call, add-on (CONF), Explicit Call Transfer (ECT), Closed User Group (CUG), Call Waiting (CW), Direct Dialling In (DDI), FreePHone (FPH), call HOLD (HOLD), Line Hunting (LH), Malicious Call IDentification (MCID), Multiple Subscriber Number (MSN), Message Waiting Indication (MWI), Outgoing Call Barring (OCB), Remote Control (RC), Selective Call Forwarding (SCF), SUB-addressing (SUB), Terminal Portability (TP), User-to-User Signalling (UUS) and Three-Party (3PTY) supplementary services.

In addition, the present document specifies the protocol requirements at the T reference point where the supplementary services are provided to the user via a private ISDN.

The present document does not specify the additional protocol requirements where the supplementary services are provided to the user via a telecommunications network that is not an ISDN.

The protocol for individual supplementary services is specified in other ETSs/ENs:

When two or more supplementary services are implemented, the protocol interactions are defined in the present document. These interactions are applicable to the telecommunication services as specified for the individual supplementary services.

The present document is applicable to equipment supporting supplementary services, to be attached at either side of the T reference point or coincident S and T reference point when used as an access to the public ISDN.

Further parts of the present document specify the method of testing required to identify conformance to the present document.