scope:

This ETS defines the stage two for the videotelephony teleservice of the pan-European Integrated Services Digital Network (ISDN) as provided by European public telecommunications operators. The stage two description identifies the functional capabilities and the information flows needed to support the service description. The stage two description also identifies user operations not directly associated with a call (see CCITT Recommendation I.130 [1]).

This ETS is specified according to the methodology specified in CCITT Recommendation Q.65 [2].

In addition, this ETS does not specify the requirements where the service is provided to the user via a private ISDN. This ETS does not specify the requirements for the allocation of defined functional entities within a private ISDN; it does, however, define which functional entities may be allocated to a private ISDN.

This ETS does not specify the additional requirements where the service is provided to the user via a telecommunications network that is not an ISDN.

The videotelephony teleservice provides a user with a symmetrical, bi-directional real-time, audiovisual teleservice in which speech and moving pictures are interchanged by means of one or two B channels in the ISDN network; the picture information transmitted is sufficient to reproduce fluid movements.

Procedures for the correlation of two independent connections within the same videotelephony call are outside the scope of this ETS. This places responsibility on the user of this service to avoid situations where certain supplementary services are being used, and also situations where multiple calls are being presented to the same user at the same time.

This ETS is applicable to the stage three standards for the ISDN videotelephony teleservice. The term "stage three" is also defined in CCITT Recommendation I.130 [1]. Where the text indicates the status of a requirement, i.e. as a strict command or prohibition, as authorisation leaving freedom, as a capability or possibility, this shall be reflected in the text of the relevant stage three standards.

Furthermore, conformance to this ETS is met by conforming to the stage three standards with the field of application appropriate to the equipment being implemented. Therefore, no method of testing is provided for this ETS.