[GreenKeys] TTY/TDD

[John Nagle]

> Subject: [GreenKeys] TTY
> 
> Is there a difference between the TTY/TDD machines the deaf  and a teletype 
> machine? Can the TTY be programmed to act as a teletype machine?

    See the Wikipedia article,

http://en.wikipedia.org/wiki/Telecommunications_device_for_the_deaf

    Classic TDD devices are indeed 45.45 baud Baudot machines, and
can talk to Teletype Model 12/15/28 machines with appropriate modems.
TDDs use an FSK half-duplex modem, one which goes silent when nothing
happens for a few hundred milliseconds.

    Newer TDD devices use V.18, which can drop down to the old protocol
but will negotiate something full duplex and faster if talking to another
V.18 modem.

    Unless you have some desire to use retro technology, though, you're
better off getting a program that makes a PC emulate a teletype machine.
TDDs aren't user-programmable devices. They're deliberately made simple,
inflexible, and reliable.

					John Nagle