Filled on behalf of RQTF - based on team discussion. @jasonjgw to specify better in future RQTF calls.

Overview of Total Conversion as specified by ITU https://www.itu.int/en/ITU-T/studygroups/com16/accessibility/Pages/conversation.aspx

A Total Conversation service is an audiovisual conversation service providing bidirectional symmetric real-time transfer of motion video, text and voice between users in two or more locations. This real time text differs from instant messaging systems because it is the transmission bi-directionally of one character at a time. This gives the user the feel of real-time communication, just like voice or video systems that transport streaming media over IP. The concept is aimed at providing for rich media real time conversation for all people and for varying situations. This includes but is not limited to people that are disabled in some way, e.g. the deaf or hard of hearing, blind etc, but also people who find themselves in a situation where the complementing media video, real-time text and voice together fulfills the conversation needs much better than only voice.

Total Conversation is an ITU service description in ITU-T Rec. F.703 and covers videophone with real time text. Ideally all videophones should offer "Total Conversation", but in many cases only video and audio are provided. F.703 is useful not only for the disabled but for anyone who can benefit from the textual back-up of for example technical data, language translations, verbal or signed conversations. It has uses for people who are not only deaf or disabled but people who can’t communicate in either of the two mediums or do not have the command of the spoken language used. Total Conversation’s use is useful to document factual information within videophone calls (e.g. phone numbers and addresses) without searching for pen and paper. An example would be to get a flight booking reference when making a travel arrangement.