A Teletype (TTY) refers to an electromechanical typewriter that can be used to communicate typed messages from point to point and point-to-multipoint over various kinds of communications channels. Teletypes were used before modern computers and terminals came into being. They were a significant component in early communication and computing technology, allowing users to interact with early computer systems and transmit messages over long distances. Teletypes are the precursors to modern-day terminals and keyboards.

Here are some key aspects of Teletype machines:

  1. Communication:
    • Teletypes could transmit and receive typed messages over telegraph and telephone lines.
    • They were commonly used for telegraphy, which is the long-distance transmission of textual messages without the physical exchange of an object bearing the message.
  2. Components:
    • A standard Teletype machine consists of a keyboard, printer, and communication interface (usually using a serial line).
    • The keyboard is used for typing messages, the printer for printing received messages, and the communication interface for transmitting and receiving messages over a communication line.
  3. Coding Systems:
    • Teletypes used character encoding systems like Baudot code and later ASCII to represent characters as sequences of bits that could be transmitted over communication lines.
  4. Operation:
    • When a key is pressed on the keyboard, the corresponding code is transmitted over the communication line.
    • When a code is received over the communication line, the corresponding character is printed on the printer.
  5. Interaction with Computers:
    • Teletypes were used as input/output devices for early computers before the advent of video terminals.
    • Users could enter commands and data by typing on the keyboard, and the results would be printed on paper.
  6. Legacy:
    • The term “Teletype” is still used in modern times to refer to text-only interfaces and terminals.
    • TTY ports and TTY mode in Linux and other Unix-like operating systems are named after Teletype machines, reflecting the historical role that Teletypes played in the development of computer user interfaces.

Teletypes have historical importance as they paved the way for the development of interactive computing and modern telecommunications systems.