TeleType

Teletype, short for teletypewriter, designates a family of electromechanical typewriters capable of sending and receiving printed text over long distances via telegraph or telephone networks. A teletype machine converts keyboard input into electrical signals and prints received signals on paper. Early teletype systems commonly used the Baudot code, a five-bit teleprinter code with shift states to switch between letters and figures; later devices adapted ASCII and other codes.

Operation and hardware: Typing produces electrical pulses that travel over a line to a distant teletype, which prints the corresponding characters. Many machines could also punch or read paper tapes for storage. Transmission was asynchronous and typically ran at modest speeds, yielding tens of words per minute depending on code and line conditions. Connections could be dedicated circuits, telephone lines, or telex networks such as TWX and Telex.

History and usage: Teletype machines emerged in the early to mid-20th century and were widely used by news agencies, businesses, military, and early computer centers. Popular models such as the Model 33 and Model 35 served as user terminals and printers for mainframes and minicomputers. With the rise of video displays and digital networks, the use of hard-copy teleprinters declined from the 1970s onward, though their influence persisted in computing culture.

Legacy: The acronym TTY remains in computing as a generic term for text input/output devices and as a reference to terminal interfaces, including Unix and Linux device files such as /dev/tty. Surviving teletype machines are preserved in museums and collections as artifacts of early real-time data communication, and the technology laid groundwork for automated telecommunications and networked computing.