Thread Subject: Re: TTYs
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From: Gregg Vanderheiden
Date: Tue, Jan 09 2007 9:05 AM
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I see you were starting with the assumption that all Gov would be IP
therefore only need to think about the IP side. That's interesting. There
are government outposts all over the US including ranger stations etc. But
I think that it is likely that all will have IP or it will be something like
a ranger tower and no something we need to address (probably communicate by
radio for example).
So I think for 508 we may indeed be able to forget TTY. Interesting.
We still have 255 though to thing about. And that is everyone's phone. So
for 255 we still have to think of what to do for analog phones (and people
who have them).
I think we should consider guidelines that says
For PSTN products - blah blah blah
For IP based telecom products - IP text etc.
I still would like to find some way of retiring TTYs either now or when
their number gets small enough that they are more trouble to accommodate
than useful. Anyone interested in exploring that technical, logistical
problem contact me offline (don't want to tie up this list). But it would
be very nice to figure out how to retire them now that it is a matter of
attrition - with no viable solution for PSTN. Something that would
eliminate the gateway problem would be very welcome by industry.
RE at IP Text standard.
Actually - there is agreement for SIP based telephony (which is what VoIP is
predominantly). T-140. There are a pair of complementary transport
protocols being discussed. Audio/t140 and Text/140. both are T-140 and
both are sent digital. Audio/t140 just has its packets labeled as audio
even though they are text - for technical reasons.
For this group - I think we can just talk about using T-140 and wait a bit
before we specify the transport protocol.
ALSO we may use the sufficient method here.
Finally, we should also allow any reliable code and transport to be used on
a closed system as long as it is translated to T-140 in the standard
protocol when it hits the open IP network.
Gregg C Vanderheiden Ph.D.
> -----Original Message-----
> From: = EMAIL ADDRESS REMOVED =
> [mailto: = EMAIL ADDRESS REMOVED = ] On Behalf Of
> Jim Tobias
> Sent: Tuesday, January 09, 2007 4:58 AM
> To: 'TEITAC Telecommunications Subcommittee'
> Subject: Re: [teitac-telecom] TTYs
> Gregg wrote:
> > Don't understand. The gateway is between two things.
> > usually in these
> > discussions it is between IP and PSTN. The gateway can
> > keep TTY from
> > getting on to the IP network (where IP text should be used).
> Gateway: PSTN TTY on one side; IP text on the other. Gateway
> must also accomplish call supervision and call routing.
> Agencies could choose to have their own gateway, or use a
> federal-wide or public gateway.
> Another wrinkle Paul explained to us yesterday is the fact
> that there is no agreement yet on what IP text protocol to
> use. If our recommended regs stick to a functional
> description -- saying only that IP text needs to be
> transported between the gateway and the agency's system -- we
> can ignore the protocol issue. Let's say that different
> agencies select different protocols. Then the gateway can,
> based on what "number" is requested by the TTY user on the
> outside PSTN, send the IP traffic consistent with that
> agency's choice.
> Gregg wrote:
> > But you still have to use TTY on the PSTN as long as there
> is a PSTN.
> > No?
> Are you referring to general public practices, or what
> federal agencies are doing?
> Agencies are obviously free to purchase new analog phone
> systems, but I doubt any are doing this. This distinction
> (actually, among 3 options: analog, non-IP digital, and
> IP) can be represented in our recommended standards by
> referring to the functional description ("transport text,
> including protocol conversion if necessary") at the top
> level, then indicating the sufficient techniques for all the
> In the final analysis, a PSTN TTY gateway may be the best way
> to smooth the migration path beyond Baudot, because it allows
> the last TTY users to continue to use their preferred method,
> but reduces the costs (direct and indirect) of compatibility
> with the growing non-Baudot text world.
> (A back-of-the-envelope calculation of total TTY US traffic
> in the busy hour shows that it could easily be accommodated
> on a very small server indeed. As usual, there are much
> bigger issues on the non-tech side: dialing plans, TRS
> integration, etc.)
> Paul also briefed us on the international scene regarding the
> many incompatible TTY protocols. To be a bit visionary, a
> gateway could address this by simply translating
> analog-to-analog protocols so the British and French deaf
> communities could communicate more easily.
> Jim Tobias
> Inclusive Technologies
> = EMAIL ADDRESS REMOVED =
> +1 732.441.0831 voice/tty
> skype jimtobias
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