scope:

The present document is applicable to the stage three of the telephony 7 kHz and videotelephony teleservices 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 specified in ITU-T Recommendation I.411 [8] by means of the Digital Subscriber Signalling System No. one (DSS1) protocol. EN 300 267-1 [3] provides the protocol specification and EN 300 267-2 [4] the Protocol Implementation Conformance Statement (PICS) proforma specification. Stage three identifies the protocol procedures and switching functions needed to support a telecommunications service (see ITU-T Recommendation I.130 [7]).