Teleprinter

A teleprinter, also known as a teletypewriter or TTY, is an electromechanical device that can input text from a keyboard, transmit it over a communications channel, and print received text on paper. It combines a keyboard, a printer, and a line interface to automate long‑distance text messaging. Teleprinters were widely used in business, government, journalism, and early computing to send and receive documents and notices.

Operation and technology: Teleprinters encode characters using codes such as Baudot (ITA2), a five‑bit character set with shifts to access letters and figures. Later devices used variants and, in some cases, ASCII. Transmission was typically asynchronous serial data over telephone lines, leased lines, or other dedicated circuits. The sender would type a message, the teleprinter would punch or encode the characters for transmission, and the remote machine would decode and print the received text. Early systems could operate at low speeds by modern standards, with baud rates often in the tens of baud range.

Networks and usage: Teleprinters formed the core of early telex networks, which linked many remote sites for two‑way messaging. They were common in newsrooms for wire service copy, in offices for internal and inter‑office communications, and in government and military contexts for official messages. Teleprinters also played a role in early computing, where mainframes or minicomputers used teletype devices as time‑sharing terminals.

Decline and legacy: With the rise of digital networks, computer terminals, fax, and email, traditional teleprinters largely disappeared from everyday use by the 1980s and 1990s. Some legacy devices remain in museums or hobbyist operation, and the term TTY continues to be used for terminal interfaces in computing.