RTT - Real-Time Text

Real-Time Text is a feature on a fixed or mobile telephone that allows users to communicate through the use of text as it is typed. It differs from Instant Messaging (IM) and mobile texting (SMS) in that the characters appear one-by-one, in near real-time, in the same pace as they are typed and not as a block of text after it is written. This way of text communications makes its much more natural, and closer to voice communications than other text based communications services as IM and SMS.

Real-Time Text is especially of importance for deaf people as an alternative for voice communications. However, it can also be of use for other, non-deaf, people as a valuable alternative, because of its more natural bi-directional flow of text compared with the “type-send-wait-read response-type reply” technology of IM and SMS.

Real-Time Text streaming text, on a character by character basis, is possible using different standards and protocols. Real-Time Text over Internet (IP) networks uses the Session Initiation Protocol (SIP) and the Real-Time Text transport standard as currently described in IETF RFC 4103.

This framework is compatible with voice over IP (VoIP) and Video over IP. It also builds upon, and is compatible with, the high-level user requirements of deaf, hard of hearing, and speech-impaired users, as described in RFC 3351.

Real-Time Text can also be implemented, and is used, on other infrastructures, such as the analogue telephone network (PSTN).

See also
External links