scope:

The present document specifies the stage three of the Line Hunting (LH) supplementary service for the pan-European Integrated Services Digital Network (ISDN) as provided by the European public telecommunications operators at the T reference point or coincident S and T reference point (as defined in ITU-T Recommendation I.411 [13]) by means of the Digital Subscriber System No. one (DSS1). Stage three identifies the protocol procedures and switching functions needed to support a telecommunications service (see CCITT Recommendation I.130 [7]). 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.