[GreenKeys] Teletype Devices for the Deaf (TDD)

[Charles Ring, W3NU]

Gary Chatters wrote:

> 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
>

is this standard still in use now with the electronic TDD devices, and are the
old machines/modems still compatible?