Real-time text (RTT) is text transmitted instantly as it is being typed or created. Recipients can immediately read the message while it is being written, without waiting.
Real-time text is used for conversational text, in collaboration, and in live captioning. Technologies include TDD/TTY devices for the deaf, live captioning for TV, a feature enhancement in instant messaging, captioning for telephony/video teleconferencing, telecommunications relay services including ip-relay, transcription services including Remote CART, collaborative text editing, streaming text applications, next-generation 9-1-1/1-1-2 emergency service. Obsolete TDD/TTY devices are being replaced by more modern real-time text technologies, including ip-relay and instant messaging.
During 2012, the Real-Time Text Taskforce (R3TF) designed a standard international symbol to represent real-time text, as well as the alternate name Fast Text to improve public education of the technology.
Use over instant messaging
While standard instant messaging is not real-time text (the message is only sent at the end of a thought, not while it is being composed), a real-time text option is found in some instant messaging software, including AOL Instant Messenger's "Real-Time IM" feature. Real-time text is also possible over any XMPP compatible chat networks, including those used by Apple iChat, Cisco WebEx, and Google Talk, by using appropriate software that has a real-time text feature. When present in IM programs, the real-time text feature can be turned on/off, just like other chat features such as audio. Real-time text programs date at least to the 1970s, with the talk program on the DEC PDP-11, which remains in use on Unix systems.
(Real-time text programs can also have a feature that allows the real-time text to be "turned-off" and the program then acts like standard IM. This might be done if the person wants to paste and edit something before transmission or to assemble to edit text carefully and review it before transmission. )
Use by the deaf
Real-time text is frequently used by the deaf, including in IP-Relay services and TDD/TTY devices. Real-time text allows the other person to read immediately, without waiting for the sender to finish composing their sentence/message. This allows conversational use of text, much like a hearing person can listen to someone speaking in real-time.
Captioned telephony is the streaming of real-time text captions in parallel with speech on a phone call. This is used by people who are hard of hearing to allow them to have the full benefit of listening as best they can, hearing all the intonation etc in speech, yet have the captions for those words they cannot hear clearly enough. In the United States, captioned telephony is one of the free relay services that is available to anyone who is hard-of-hearing. Originally developed for use on the analog phone systems (where it requires a special phone) it is now available over IP using standard devices.
Use in collaboration
Collaborative real-time editing, including Apache Wave and Etherpad, is the utilization of real-time text for shared editing, rather than for conversation. Split screen chat, where conversational text appears continuously, is also considered real-time text.
Captioning, Transcriptions and other uses
Real-time text is used in closed captioning and when captions are being streamed live continuously during live events. Transcription services including Communication Access Real-Time Translation frequently use real-time text, where text is streamed live to a remote display. This is used in court reporting, and is also used by deaf attendees at a conference. Also, real-time text provides an enhancement to text messaging on mobile phones, via real-time texting apps.
Real-time text protocols
According to ITU-T Multimedia Recommendation F.703, Total Conversation defines the simultaneous use of audio, video and real-time text. An instant messaging program that can enable all three features simultaneously, would be compliant. Real time text is an important part of it.
- Reach 112 emergency service trial involving real-time text
- realtimetext.org - Real Time Text Taskforce (R3TF)
- Standard International Symbol for Real-Time Text
- AOL Instant Messenger "Real-Time IM"
- ITU-T T.140 - Protocol for multimedia application text conversation
- IETF RFC4103 - RTP Payload for Text Conversation
- IETF RFC5194 - Framework for Real-Time Text over IP Using SIP
- XEP-0301 - In-Band Real-Time Text
- ITU-T Rec. F.703 - Multimedia conversational services