scope:

This standard specifies the stage three of the Calling line Identification Restriction (CLlR) 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 CCITT Recommendation 1.411 [1]) by means of the Digital Subscriber Signalling System No. one (DSS1). Stage three identifies the protocol procedures and switching functions needed to support a telecommunications service (see CCITT Recommendation 1.130 [2]).

In addition this standard specifies the protocol requirements at the T reference point where the service Is provided to tt\e user via a private ISDN.

This standard 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 CLIR supplementary service enables the calling party to prevent presentation of its ISDN number to the called party.

The CLIR supplementary service is applicable to all telecommunication services.

Further part(s) of this standard will specify the method of testing required to Identify conformance to this standard.

This standard is applicable to equipment supporting the CllR 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.