The present document specifies procedures to support basic bearer services and supplementary services defined for the
pan-European Integrated Services Digital Network (ISDN) as provided by the European public telecommunications
operators by means of the Signalling System No.7 protocol for the ISDN User Part (ISUP).
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.
Although the present document applies only to the international interconnection, the specification of functions, formats
and codes of messages and signals, and actions performed at originating and destination local exchanges are retained.
Formats, codes and procedures marked for national use are included for informative purposes for the international
interface specification. If these items so marked are supported within a national network and operators network, then it
is proposed that they shall be supported in this manner.
Items in the present document marked "not required" are not required to be supported.
NOTE: In the case where a national signalling system behaves differently, the international gateway exchange is
to support both the concerned national and international network.
The present document is compatible with ETS 300 121 [2] (ITU-T Recommendation Q.767).
Descriptions of interworking with ITU-T Blue Book (1988) exchanges are informative only.