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

Edward Tie famtie at xs4all.nl
Mon Jul 9 14:57:16 UTC 2012


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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