"The present document defines the stage one of the Connected Line Identification Presentation (COLP) supplementary service for the pan-European Integrated Services Digital Network (ISDN) as provided by European public telecommunications operators. Stage one is an overall service description from the user's point of view (see CCITT Recommendation I.130 [1])@ but does not deal with the details of the human interface itself. The present document defines the interworking requirements of private ISDNs with the public ISDN. In addition the present document specifies the base functionality where the service is provided to the user via a private ISDN. The present document does not specify the additional requirements where the service is provided to the user via a telecommunications network that is not an ISDN but does include interworking requirements of other networks with the public ISDN. Interactions with supplementary services not listed in clause 8 are outside the scope of the present document. Charging principles are outside the scope of the present document. The COLP supplementary service provides the calling party with the possibility to receive identification of the connected party. The COLP supplementary service is applicable to all telecommunications services. The present document is applicable to the stage two and stage three standards for the ISDN COLP supplementary service. The terms ""stage two"" and ""stage three"" are also defined in CCITT Recommendation I.130 [1]. Where the text indicates the status of a requirement@ (i.e. as strict command or prohibition@ as authorization leaving freedom@ or as a capability or possibility)@ this shall be reflected in the text of the relevant stage two and stage three standards. Furthermore@ conformance to the present document is met by conforming to the stage three standards with the field of application appropriate to the equipment being implemented. Therefore no method of testing is provided for the present document."