This Recommendation specifies the usage of all protocols and supplementary services up to and including layer 3 for syntax-based Videotex terminal equipment in the ISDN. The scope of this Recommendation is limited to circuit switched calls using the 64 kbit/s unrestricted digital information bearer capability and the DTEDTE case of the network layer peer entities in B-channel connection. This standard is applicable to terminal equipment supporting the syntax-based Videotex using either basic access or primary rate access to the ISDN. In this context, a terminal equipment is either a Videotex terminal, a Videotex service centre, a Videotex access point or a Videotex host. This Recommendation is based on other CCITT Recommendations and International Standards and where necessary, it adds new or other requirements as application rules.