CORRIGENDUM Integrated Services Digital Network (ISDN); Call Hold (HOLD) Supplementary Service Digital Subscriber Signalling System No. One (DDS1) Protocol Part 1: Protocol Specification (Corrigendums 1993 and 1994 - Withdrawn)
This standard specifies the stage three of the Call Hold supplementary (HOLD) 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) protocol. Stage three identifies the protocol procedures and switching functions needed to support a telecommunications service (see CCITT Recommendation I.130 [2]) . In addition this standard specifies the protocol requirements at the T reference point where the service is provided to the 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 HOLD supplementary service allows a user to interrupt communications on an existing call and then subsequently@ if desired@ re-establish communications. The HOLD supplementary service is applicable to all circuit-switched telecommunication services. Further part(s) of this standard specify the method of testing required to identify conformance to this standard. This standard is applicable to equipment@ supporting the HOLD 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.