The present document specifies the stage three of the Calling Line Identification Presentation (CLIP) supplementary
service 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 [1]) 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 [2]).
In addition the present document specifies the protocol requirements at the T reference point where the service is
provided to the user via a 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 CLIP supplementary service provides the called party with the possibility to receive identification of the calling
party, and is applicable to all telecommunication services.
Further parts of the present document specify the method of testing required to identify conformance to the present
document.
The present document is applicable to equipment supporting the CLIP supplementary service, to be attached at either
side of a T reference point or coincident S and T reference point when used as an access to the public ISDN.