ITU Standards
by Michael Day, Product Manager for British Telecom TextDirect
Evolution of textphones in UK
Historically, The UK used several different textphone protocols,
including V.23, V.21, and Baudot. Devices that used the same protocols
didn't always work together, because there was no standard
implementation. And devices using different protocols certainly didn't
work together. It's even worse if you consider all of Europe.
We worked with the Royal National Institute for the Deaf (RNID) to
address text phone issues. About 1990 we decided to have a 24/7 relay
service. Later we thought that there was a need for text phone users to
be able to use the phone network better.
BT TextDirect
TextDirect is a way to get text phone users more information, so they
can better interact with the phone system. One result is that it
improves access to the relay system. (Note that BT TextDirect is not
just a relay system, but it includes a relay system.)
BT TextDirect Features
- Call setup information is in text; the information coming back from
the system is in text.
- The system provides 24/7 access to relay.
- The system allows a user to start a conversation without using the
relay service and bring the relay in later if it's needed.
- The system provides improved compatibility; textphones can talk to
textphones that use other protocols, because TextDirect sits between
them.
- The system provides a caller return feature, which allows a user to
determine the number of the last person to call.
- Calls may be placed to or from anywhere in the UK. (Note that there is
still a problem with mobile phones.)
- The system includes a cost rebate to make up for the fact that typing
is slower than talking.
- The system includes a help desk.
How Does it Work?
- Textphone users dial 18001 before all calls, regardless of who they
are calling.
- Voice users call 18002
- The Textphone Emergency number is 18000.
- relay assist service - you don't get an operator unless you need one,
but this feature allows you to get one from the start.
- International access - a user can access the system from anywhere in
world.
- If the voice user switches to a TTY the relay operator drops out.
Lessons Learned
The V.18 protocol was done on paper before we built anything. We
still have problems with things like music on hold, answering machine
beeps, even some voices. Because V.18 is designed to talk so many
protocols, it is very flexible. A resulting problem is that it gets
fooled by other things, including voices.
What drove the need to develop a new system?
- Communication involves both voice and text, and we need to make
sure everyone can talk to everyone else.
- There are many new and potential mainstream products that are
potential textphones, e.g. computers and PDAs.
Solutions
- Internet Protocol will become the dominant transport mechanism.
- Any system must support multiple implementations (dial-up, broadband,
etc.)
- We can do it now.
- We must design and build for the future
The Textphone Gateway
- Talk to the gateway to talk to the world; textphones don't need to
talk to each other; they only need to talk to the gateway.
- Allows a textphone to talk to almost any device.
- Farther in the future, we may have multiple gateways that talk to each
other. This concept facilitates international textphone communications.
- Each gateway supports its local protocol.
- Each gateway has all the intelligence needed for all the devices to
communicate.
- Legacy textphones are not excluded; we can move to IP and still
support legacy hardware, because the gateways take care of it.
What's next?
- Improved functionality
- Improved availability
- We need international agreements to ensure compatibility
Q: what kinds of calls do you get in the help center?
A: Usually "how to use it" questions from new users - either
people with hearing loss or hearing people who are complying with
anti-discrimination law.
Q: You gave a demo of how flow progresses. How fast is the relay
conversation compared to a voice conversation?
A: The system has the problem of typing, as in the US. I think the
future includes voice recognition. I think it would have to be in the PC
initially.
Q: What types of problems are you having with mobile networks?
A. It's a bit complicated. A person calls and a voice connection is made
to TextDirect. That triggers the billing to the mobile network. We don't
want to bill unless the call succeeds. For landlines, we provide a
billing record for each call, but 24 hours later. Mobile phones need to
know now, because some are pay as you go. Mobile networks in the UK
don't currently have to provide textphone access.
Q: This question is related to the gateways. On September 11 in the
US the cell towers were jammed; they were just too busy. Would that be a
problem with the gateways in an emergency?
A There are actually two gateways and they work as one. But the network
can get clogged up. We've had problems, yes. What we can do is stop
calls at the local exchange. The reason we have a special number for
emergencies is so the network will try to complete those calls first.
Comment: The problem of emergency calls is now being looked at by the
ITU; they want to give priority to emergency calls, and we are talking
to them about textphone users.
