The present document defines the stage one of the Completion of Calls on No Reply (CCNR) supplementary service for
the pan-European Integrated Services Digital Network (ISDN) as provided by European public telecommunications
operators. Stage one is an overall service description from the users point of view
(see CCITT Recommendation I.130 [1]), but does not deal with the details of the human interface itself.
The present document defines the interworking requirements of private ISDNs with the public ISDN.
In addition, the present document specifies the base functionality where the service is provided to the user via a private
ISDN.
The present document does not specify the additional requirements where the service is provided to the user via a
telecommunications network that is not an ISDN but does include interworking requirements of other networks with the
public ISDN.
Interactions with supplementary services not listed in clause 7 are outside the scope of the present document.
Charging principles are outside the scope of the present document.
The CCNR supplementary service enables user A, encountering a destination B which does not answer the call
(No Reply), to have the call completed without having to make a new call attempt when the destination B becomes not
busy after having initiated an activity.
The CCNR supplementary service is applicable to all circuit-switched telecommunications services with the following
exceptions:
a) call 2 of the videotelephony teleservice (see ETS 300 264 [8]);
b) call 2 of the audiographic conference teleservice (see ETS 300 675 [10]);
c) call 2 and subsequent calls of videoconference teleservice (see ETS 300 678 [11]);
d) all other circuit-switched telecommunication services requiring the use of more than one B-channel.
The present document is applicable to the stage two and stage three standards for the ISDN CCNR supplementary
service. The terms "stage two" (...abbreviated)