The present document specifies the stage three of the videotelephony, telephony 7 kHz, audiographic conference and
videoconference 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 defined in ITU-T Recommendation I.411 [6]) 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 telecommunication service
(see CCITT Recommendation I.130 [5]).
In addition, the present document specifies the protocol requirements at the T reference point where the service is
provided to the user via a private ISDN.
The present document does not specify the additional protocol requirements where the service is provided to the user via
a telecommunication network that is not an ISDN.
For the telephony 7 kHz, videotelephony, audiographic conference and videoconference teleservices, the present document specifies procedures for commencement of the in-band protocol by normative reference to the relevant in-band protocol ETSs.
The present document also specifies additional procedures to those required to support basic call in EN 300 403-1 [25]
in order to support the four teleservices described in the present document. These additional procedures may be used to support other basic telecommunication services.
The telephony 7 kHz teleservice is a real-time teleservice in which speech (7 kHz or 3,1 kHz bandwidth) can be interchanged using one circuit-mode 64 kbit/s connection.
The videotelephony teleservice is a real-time, audiovisual teleservice in which speech and moving pictures are
interchanged by means of one or two 64 kbit/s circuit-mode connections in the ISDN. The picture information transmitted is sufficient for adequate representation of fluid movements of a pe (...abbreviated)