Ateletypewriter (TTY; also called ateletype orteleprinter) is adevice that sends atyped message to another place. A teletypewriter has atypewriter keyboard, a localprinter (so the user can see what has been typed) and atransmitter. Messages can be sent over wires orradio waves. Teletypes were used mostly in the early to mid-20th century. They were developed to improvetelegraphs, some of which also used keyboards, though not typewriter keyboards.
Though teleprinters have been replaced by other technologies, TDDs (Telecommunications Devices for the Deaf), which are based on the idea and design of teletypes, are still used these days. Not all people who aredeaf, hard of hearing, or speech-impaired have switched to usinginstant messaging ortexting or other modern services. Many still type messages back and forth to one another by TDD.
