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

Mark Rejhon markybox at gmail.com
Mon Jul 9 15:05:20 UTC 2012

I propose a shorter section added to Interoperability, since it is listed
as one of the Requirements (TTY alternative) in Section 2, so it is very
prudent that I expand on how it's accomplished, by adding this section to

*8.3 TTY and Textphones*
*Real-time text is implemented in assistive telephone devices that operate
on the PSTN (e.g. TTY in North America, textphone in Europe), using various
text telephone modulation protocols such as those specified in ITU-T V.18
and its annexes (e.g. Baudot, DTMF). It is possible to implement gateways
between them and XEP-0301 based real-time text, and can be combined with an
audio protocol such as XEP-0166 (e.g. for Voice Carry Over). *

It satisfies everyone concerns I hope, because:
1. Its first sentence is jargon-free
2. It is reasonably short.
3. I use "various text modulation protocols" to include any possible text
modulation protocols, not just those in V.18 (I only use the phrase "such
as" -- which keeps the door open to anything)
4. Any audio protocol may be used.
5. Further implementation details are left out of this; and best covered by
a FAQ site (like the one I eventually plan to create)

On Mon, Jul 9, 2012 at 10:57 AM, Edward Tie <famtie at xs4all.nl> wrote:

>  Op 09/07/2012 16:30, Gunnar Hellström schreef:
> On 2012-07-09 13:31, Edward Tie wrote:
> 8.3 Textphones and TTYs in the PSTN (Informational)
> Real-time text is also implemented in the PSTN, through various text
> telephone modulation protocols specified in ITU-T V.18 *or V.22 or 300
> baud ASCII or DTMF.*  It is possible to implement gateways between audio
> and XEP-0301 based real-time text in IP networks and textphones (called TTY
> in North America)  based on V.18* or V.22 or *any of its Annexes in the
> PSTN. When designing such gateways, the limitations in speed, transmission
> direction, character sets and media simultaneity valid for these textphone
> protocols must be taken into consideration as well as the user need to be
> able to at least alternate between audio and real-time text during the
> call.
> Edward,
> We shall not try to tell the whole story about PSTN text telephony (and
> TTY) in this XMPP document.
> I rather want to follow Peter's advice to reduce it.
>  XEP-0301 has its important role as improvement of user experience of
> XMPP text messaging. Details on interoperability should be specified
> elsewhere.  I suggest a very brief paragraph to be kept about legacy
> textphone interoperability. (coming soon)
> ---------------------------------------------------------------------------------------------------------
> Anyway, for your info,
> ITU-T V.18 has one annex for each of the legacy textphone protocols:
> Baudot (=TTY), V.21, DTMF, V.23(Minitel and even Prestel), Bell
> 103("ASCII"), and even for V.18 itself. You wanted to add V.22 to the list.
> I know it is in use in The Netherlands, but The Netherlands never wanted it
> to be included in V.18.
> yes. it's true
> So, V.22 is not standardized anywhere as a textphone transport, and as I
> understand it,
> Only Dutch next generation textphone (HGT teksttelefoon) supports V.22
> (1200) and V.22bis. It called TDD.
>  See dutch summery:
> http://home.planet.nl/~hgtgm000/Downloads/TT_appendix_A_en_B.pdf
>  all Dutch V.22 textphones can also do automatic switching to DTMF based
> text telephony.
> Yes. Dutch old generation textphones (Goedhart visicom and PTT
> teksttelefoon) supports only DTMF.
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