scope:

This ETS specifies the system requirements for a videotelephone using one or two B-channels, when connected to the S point or coincident S and T reference point of the pan-European Integrated Services Digital Network (ISDN). These requirements ensure end-to-end compatibility of terminals supporting the videotelephony teleservice to ETS 300 264 [9].

Conformance to this ETS allows interworking with terminals supporting telephony 3,1 kHz teleservice to ETS 300 111 [3], telephony 7 kHz teleservice to ETS 300 263 [8], terminals to CCITT Recommendation G.725 [13], and Public Switched Telephone Network (PSTN) telephony. Interworking with other audiovisual terminals can take place if their operation on one or two B-channels is according to this ETS.

This ETS is applicable to terminal equipment and other equipment supporting the videotelephony service, such as multipoint conference units.

Interworking with terminals not connected to an ISDN may be possible if one or two 64 kbit/s (unrestricted or restricted) digital channels can be established between the two terminals.

The inband signalling procedures are described in ETS 300 143 [6], and the syntax for these procedures is defined in ETS 300 144 [7]. The video coding algorithm is described in ITU-T Recommendation H.261 [5].

NOTE: Interworking with terminals to CCITT Recommendation G.725 [13] may be restricted to mode 0.