TTD

Telecommunications Device for the Deaf
TDD
Telecommunication Display Device
TTD

   <communications> (TDD) A terminal device used widely by deaf
   people for text communication over telephone lines.

   The acronym TDD is sometimes expanded as "Telecommunication
   Display Device" but is generally considered to be derived from
   "Telecommunications Device for the Deaf".  The deaf themselves
   do not usually use the term "TDD", but prefer simply "{TTY}"
   -- possibly the original term.  The ambiguity between this and
   the other meanings of "{TTY}" is generally not problematic.
   The acronym "TTD" is also common [Teletype for the deaf?].

   The standard most used by TDDs is reportedly a survivor of
   {Baudot code}.  It uses {asynchronous} transmission of 1400 Hz
   and 1600 Hz tones at 45.5 or 50 {baud}, with one {start bit},
   5 data bits and 1.5 {stop bits}.  This is generally
   incompatible with standard {modems}.

   A typical TDD is a device about the size of a small {laptop
   computer} (resembling, in fact, a circa 1983 Radio Shack
   {Model 100} computer) with a {QWERTY keyboard}, and small
   screen (often one line high, often made of an array of
   {LEDs}).  There is often a small printer for making
   transcripts of terminal sessions.  An {acoustic coupler}
   connects it to the telephone handset.

   With the falling cost of {personal computers} and the
   widespread use of {Internet} {talk} systems, there is now
   little reason to use this {Stone Age} technology.

   [Standards?  {i18n}?]

   (2006-10-08)