[VoiceOps] 711 relay

Nathan Anderson nathana at fsr.com
Wed Mar 20 18:10:50 EDT 2013

This is another great question, and one that I was also wondering about.

I know that T.140 exists, but it is not clear to me...

1) ...whether it is considered the analogue of what T.38 is in the FoIP world (T.38 is to T.30 as T.140 is to TDD?)
2) ...if #1 is true, whether any consumer-grade ATAs support T.140 in this capacity, and/or whether any IP->PSTN term providers run T.140-to-TDD gateways themselves.

T.38 basically encapsulates T.30 events, messages, and data inside of IP datagrams, but from what little I've read about T.140, it sounds more like a protocol designed to replace TDD/TTY, not encapsulate it.  Thus, gatewaying TDD to T.140 and vice-versa is a bit of a different proposition than T.38 gatewaying.

Given that TDD is relatively low bitrate, I'd wager that simply doing G.711 passthrough would work the majority of the time.  We have had some success hooking up telephone-based security systems (ADT) through our network after switching the system over to using FSK instead of DTMF (DTMF would get intercepted by the ATA and translated to out-of-band RTP events, which neither side apparently liked too much; the FSK encoding seems to work flawlessly), and that is similarly low bitrate, but calls being generated by such systems are also relatively short.

-- Nathan

-----Original Message-----
From: Eric Fort [mailto:eric.fort at gmail.com] 
Sent: Wednesday, March 20, 2013 2:58 PM
To: Nathan Anderson
Cc: voiceops at voiceops.org
Subject: Re: [VoiceOps] 711 relay

711 poses an interesting proposition for VoIP as relay services go both ways.  It's not always a voice caller dialing 711 but TDD calls as well.  Generally inbound calls get sorted by some sort of auto attendant where calls that detect some form of modem tone (TDD) signaling go to one operator and other calls are voice.  While the TDD traffic is relatively low bit rate fsk it's still modem traffic conveying digital rather than analogue data.  How is the TDD case being handled?

Eric Fort

On Wed, Mar 20, 2013 at 2:25 PM, Nathan Anderson <nathana at fsr.com> wrote:

	Question for other ITSPs out there: what are you doing for 711 TTY relay services?
	I know so little about this area it's sad.  Are we supposed to either staff our own relay staff, pass them off to a third-party relay service, or pass the calls off to a state-provided service?  Can this be done with a third-party service a-la what 911Enable and friends do for 911 PSAP routing?  What companies out there provide services like this?
	If the states you provide service in have an 800 number for connecting to a state-run relay service, can I simply translate 711 to the appropriate 800 number and terminate the 800 call as I normally would?
	Nathan Anderson
	First Step Internet, LLC
	nathana at fsr.com
	VoiceOps mailing list
	VoiceOps at voiceops.org

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