scope:

This second part of ETS 300 668 is applicable to the stage three of the User-to-User Signalling (UUS) supplementary service for the pan-European Broadband Integrated Services Digital Network (B-ISDN) as provided by European public telecommunications operators at the TB reference point or coincident SB and TB reference point (as defined in ITU-T Recommendation I.413 [8]) by means of the Digital Subscriber Signalling System No. two (DSS2). Stage three identifies the protocol procedures and switching functions needed to support a telecommunication service (see CCITT Recommendation I.130 [7[).