<hardware> /tit'ee/ (ITS pronunciation, but some Unix people say it this way as well; this pronunciation is not considered to have sexual undertones), /T T Y/ 1. teletypewriter. 2. (Especially Unix) Any terminal at all; sometimes used to refer to the particular terminal controlling a given job (it is also the name of a Unix command which outputs the name of the current controlling terminal). 3. (Unix) Any serial port, whether or not the device connected to it is a terminal; so called because under Unix such devices have names of the form tty*. Ambiguity between senses 2 and 3 is common but seldom bothersome. 4. A TDD. [Jargon File] (1995-11-23)

TeleTYpe

Berkeley Unix networking device which appears to an application program as an ordinary terminal but which is in fact connected via the network to a process running on a different host or a windowing system. Pseudo-ttys have a slave half and a control half. The slave tty (/dev/ttyp*) is the device that user programs use and the control tty (/dev/ptyp*) is used by daemons to talk to the net. (1994-11-08)

<hardware> (Nearly always abbreviated to "teletype" or "tty") An obsolete kind of terminal, with a noisy mechanical printer for output, a very limited {character set}, and poor print quality. See also bit-paired keyboard. (2000-04-02)

A teleprinter (teletypewriter, teletype or TTY) is an electromechanical device that can be used to send and receive typed messages through various communications channels, in both point-to-point and point-to-multipoint configurations. Initially they were used in telegraphy, which developed in the late 1830s and 1840s as the first use of electrical engineering, though teleprinters were not used for telegraphy until 1887 at the earliest.

<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)