The present document is applicable to the stage three of the Completion of Calls to Busy Subscriber (CCBS)
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
ITU-T Recommendation I.411 [11]) 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 ITU-T Recommendation I.130 [10]).
The present document provides the Protocol Implementation Conformance Statement (PICS) proforma for the ISDN
DSS1 CCBS supplementary service protocol as specified in EN 300 359-1 [7] in compliance with the relevant
requirements and in accordance with the relevant guidance given in ISO/IEC 9646-7 [9].
The supplier of a protocol implementation which is claimed to conform to EN 300 359-1 [7] is required to complete a
copy of the PICS proforma provided in annex A of the present document and is required to provide the information
necessary to identify both the supplier and the implementation.