[Standards] UPDATED: XEP-0301 (In-Band Real Time Text)

Edward Tie famtie at xs4all.nl
Mon Jul 9 10:08:54 UTC 2012

Op 09/07/2012 11:40, Mark Rejhon schreef:
> On Mon, Jul 9, 2012 at 2:09 AM, Edward Tie <famtie at xs4all.nl 
> <mailto:famtie at xs4all.nl>> wrote:
>     Hi Mark,
>          I want to add on history of textphone and XMPP to old
>     telephones that uses older protocols:
> Hello Edward,
> Good history -- however, this is already beyond scope of XEP-0301.
> Anybody can create an XEP-0301 gateway that converts to almost 
> anything (including any of the protocols you mention).
> One sentence will be added to satisfy this.
> http://xmpp.org/extensions/xep-0301.html#interoperability_considerations
> To just simply mention that "...a gateway can be built as a part of a 
> complete solution (i.e. with optional audio, such as to support Voice 
> Carry Over) to support any legacy protocols used by TTY and textphones 
> using various protocols including Baudot, 300 baud ASCII, DTMF, ITU-T 
> V.18, ITU-T V.22, and other text transmission protocols". (wording 
> will be refined upon consultation within R3TF including Gregg 
> Vanderheiden who helps out in this area)
> There was a lot of debate within our group (i.e. Gregg Vanderheiden) 
> about the careful choice of wording, because we need to be sensitive 
> about the "complete solution" (such as worldwide interoperability, the 
> ability to use voice, accessibility to people who don't have Internet, 
> etc).

it's now a clear history :-)

>         Protocols
>     There are many different textphone standards.
>           Baudot code
>     The original standard used by TTYs is the Baudot code
>     <http://en.wikipedia.org/wiki/Baudot_code> implemented
>     asynchronously at either 45.5 or 50 baud, 1 start bit, 5 data
>     bits, and 1.5 stop bits. Baudot is a common protocol in the US.
>           Turbo Code
>     In addition to regular Baudot, the UltraTec
>     <http://en.wikipedia.org/w/index.php?title=UltraTec&action=edit&redlink=1>
>     company implements another protocol known as Enhanced TTY, which
>     it calls "Turbo Code," in its products. Turbo Code has some
>     advantages over Baudot protocols, such as a higher data rate, full
>     ASCII <http://en.wikipedia.org/wiki/ASCII> compliance, and
>     full-duplex capability. However, Turbo Code is proprietary, and
>     UltraTec only gives its specifications to parties who are willing
>     to license it.
>           Other legacy protocols
>     Other protocols used for text telephony are European Deaf
>     Telephone (EDT) and Dual-tone multi-frequency signaling
>     <http://en.wikipedia.org/wiki/Dual-tone_multi-frequency_signaling>
>     (DTMF).
>     The ITU V series recommendations are a collection of early modem
>     standards approved by the ITU <http://en.wikipedia.org/wiki/ITU>
>     in 1988.
>       * ITU V.21 <http://en.wikipedia.org/wiki/ITU_V.21> [1]
>         <http://www.itu.int/rec/T-REC-V.21/recommendation.asp?lang=en&parent=T-REC-V.21-198811-I>
>         specifies 300 bits per second duplex mode.
>       * ITU V.23 <http://en.wikipedia.org/wiki/ITU_V.23> [2]
>         <http://www.itu.int/rec/T-REC-V/recommendation.asp?lang=en&parent=T-REC-V.23>
>         specifies audio frequency-shift keying
>         <http://en.wikipedia.org/wiki/Audio_frequency-shift_keying>
>         modulation to encode and transfer data at 600/1200 bits per
>         second.
>           V.18
>     In 1994 the ITU
>     <http://en.wikipedia.org/wiki/International_Telecommunication_Union>
>     approved the V.18
>     <http://en.wikipedia.org/w/index.php?title=ITU_V.18&action=edit&redlink=1>
>     standard [3] <http://www.itu.int/rec/T-REC-V.18/en>. V.18 is a
>     dual standard. It is both an umbrella protocol that allows
>     recognition and interoperability of some of the most commonly used
>     textphone protocols, as well as offering a native V.18 mode, which
>     is an ASCII <http://en.wikipedia.org/wiki/ASCII> full- or
>     half-duplex modulation method.
>     Computers can, with appropriate software and modem, emulate a V.18
>     TTY. Some voice modems, coupled with appropriate software, can now
>     be converted to TTY modems by using a software-based decoder for
>     TTY tones. Same can be done with such software using a computer's
>     sound card, when coupled to the telephone line.
>     In the UK, a virtual V.18 network, called TextDirect, exists as
>     part of the Public Switched Telephone Network
>     <http://en.wikipedia.org/wiki/Public_Switched_Telephone_Network>,
>     thereby offering interoperability between textphones using
>     different protocols. The platform also offers additional
>     functionality like call progress and status information in text
>     and automatic invocation of a relay service for speech-to-text calls.

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