[GreenKeys] Teletype Devices for the Deaf (TDD)

[Gary Chatters]

On Sun, 23 Feb 2003, Don Robert House wrote:

> got the machine but not the modem.  At the time I did not understand
> why the modems were different than the standard F1 and F2
> frequencies.  The only thing I can think of is they did not want them
> to be used commercially by connecting to TWX machines.
>

The TTY system for the deaf (TDD) was developed by a deaf ham, W6NRM.  One
of the primary considerations was making the modems cheap.  The TDD modems
use a single tone OOK, not FSK.  That is about as simple as you can make
it.

Gary