scope:

This first part of EN 300 052 specifies the stage three of the Multiple Subscriber Number (MSN) 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 I.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 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 equirements where the service is provided to the user via a telecommunications network that is not an ISDN.