scope:

This draft 2nd edition of ETS 300 145 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 described in ETS 300 264 [1].

This ETS is applicable in whole to Terminal Equipment (TE) supporting the videotelephony teleservice; subclauses 5.3, 6.1, 6.2 and clause 8 are also applicable to Multipoint Control Units (MCUs) using one or two B-channels.

The specific requirements which apply to a terminal in order to support various options related to videoconference and/or data transmission are specified in other documents (e.g. Draft prETS 300 483 [2]).

Conformance to this ETS allows interworking with terminals supporting the telephony 3,1 kHz teleservice described in ETS 300 111 [3], the telephony 7 kHz teleservice described in ETS 300 263 [4] and Public Switched Telephone Network (PSTN) telephony terminals. Interworking with other audio-visual terminals can take place if their operation on one or two B-channels is according to this ETS.

NOTE 1: Terminals in accordance with ITU-T Recommendation H.320 can interwork, if one or two 64 kbit/s (unrestricted or restricted) digital channels can be established between the terminals (e.g. using a remote Channel Aggregation Unit in case of a 128 kbit/s H.320 single channel terminal).

NOTE 2: Interworking with terminals according to CCITT Recommendation G.725 [5] is optional; it may be restricted to mode 0.

NOTE 3: Audio and video signal interfaces are outside the scope of this ETS.

NOTE 4: Interfaces and protocols used for optional data transmission are outside the scope of this ETS.

The in-band 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 [8].