ITU-T Q.953.5

This Recommendation specifies the stage three of the Call Completion on No Reply (CCNR) supplementary service for the Integrated Services Digital Network (ISDN) at the T reference point or the coincident S and T reference point by means of the Digital Subscriber System No. 1 (DSS1) protocol. Stage three identifies the protocol procedures and switching functions needed to support a telecommunication service. The CCNR supplementary service enables a calling user A, encountering a destination B which does not answer the call (No Reply), to be notified, when the destination B becomes not busy after having initiated an activity. If user A desires, then the network will reinitiate the call to the specified destination B. This Recommendation includes an electronic attachment containing the SDL diagrams in reprocessable SDT format.