A teleprinter (teletypewriter, teletype or TTY) is a now largely obsolete electro-mechanical typewriter which can be used to communicate typed messages from point to point through a simple electrical communications channel.
It had a very limited character set, and poor print quality. The printer was often linked to a punched tape punch and reader allowing the creation of a message stream for offline archival (i.e. save away the paper tape in some box). This was useful for situations in which access to the communication channel was at a premium.
The teleprinter evolved through a series of inventions by a number of engineers, including Royal E. House, David Edwin Hughes, Charles Krum and Emile Baudot.
Teleprinters used the 5-bit Baudot code (also known as IA2) to represent their character set.
The Baudot code was used asychronously with start and stop bits: the asynchronous code design was intimately linked with the start-stop electro-mechanical design of teleprinters. (Early systems had used synchronous codes, but were hard to synchronise mechanically).
This guide is licensed under the GNU Free Documentation License. It uses material from the Wikipedia.
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