"This European Telecommunication Standard (ETS) defines the stage one of the audiographic conference teleservice for the pan-European Integrated Services Digital Network (ISDN) as provided by European public telecommunications operators. Stage one is an overall service description from the user's point of view (see CCITT Recommendation I.130 in annex C)@ but does not deal with the details of the human interface itself. This ETS defines the interworking requirements of private ISDNs with the public ISDN. In addition@ this ETS specifies the base functionality where the service is provided to the user via 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 but does include interworking requirements of other networks with the public ISDN. Charging principles are outside the scope of this ETS. The values of the general attributes are outside the scope of this ETS. The audiographic conference teleservice is a real-time teleservice in which high quality speech@ control signals and data are interchanged using one or more circuit-mode 64 kbit/s connection(s). This ETS is applicable to the stage two and stage three standards for the ISDN audiographic conference teleservice. The terms ""stage two"" and ""stage three"" are also defined in CCITT Recommendation I.130. Where the text indicates the status of a requirement (i.e. as strict command or prohibition@ as authorization leaving freedom@ or as a capability or possibility)@ this will be reflected in the text of the relevant stage two and stage three standards. Furthermore@ conformance to this ETS is met by conforming to the stage three standard with the field of application appropriate to the equipment being implemented concerning characteristics at the user-network interface@ and by conforming to the ETS on the end-to-end characteristics appropriate to the equipment being implemented. Therefore@ no method of testing is provided for this ETS. NOTE: In the current version of this ETS the use of protocols in the ITU-T T.120 series of recommendations (see annex C) is an option. This position may be reviewed later."