Definition - What does Teletypewriter (TTY) mean?
A teletypewriter is an electromechanical typewriter that helps in point-to-point communication with the help of typed messages via a simple electrical communications channel. Teletypewriters had either built-in or linked to paper tape punching and reading machines. This allowed messages to be made and modified offline as well to be stored and retransmitted if needed in other devices or circuits.
A teletypewriter is also known as a teleprinter, teletype machine or simply a teletype.
Techopedia explains Teletypewriter (TTY)
The five-bit Baudot code was mostly used by early teletypewriters for communication. Introduced in 1922, the Model 12 was the first general purpose teletypewriter and was succeeded by the Model 14 three years later. The Model 15 was a popular teletypewriter launched in 1930 and was one of the mainstays of U.S. military communications, especially during World War II. A teletypewriter consists of a typewriter keyboard, transmitter and a local printer. Messages were capable of being transmitted over radio waves or over wires. The input device is considered as an early computer interface and was developed by Teletype Corporation. In fact, some of the earliest computers made use of teletypewriters for input as well as output.
Teletypewriters were developed to improve telegraphs, but have now been largely replaced by other technologies. However, they are still used by speed-impaired, deaf or hard of hearing people for communication.