TTY

1. Short for TeleTYpewriter, TTY is a communications setup that has a keyboard and a printer. Each time a key is pressed it is automatically printed, modern TTY machines print to the screen. Teletype machines were available in three different modes: Automatic send and receive (ASR) -- Able to send and receive, Receive Only (RO) -- only capable of receiving data and not sending, and Keyboard Send and Receive (KSR) -- TTY with keyboard capable of sending and receiving data.
2. Today, TTY is also used to describe a terminal session and/or line.

Also see: Keyboard definitions, TDD