From the Greek tele, meaning far off, and typos, meaning mark, and translating literally as markfar off. A printing telegraph system that replaced the sending key with a typewriter-like keyboard and the receiving sounder with a teleprinter. Western Union introduced teletypewriter service in 1923 so that companies could link branches and even join other companies in private text messaging over leased privateline networks.Teletype service was heavily used by banks, telephone companies, electric utilities, and others into the early 1970s. Teletypewriter (TTY) service, also known as Telecommunications Device for the Deaf (TDD) in the United States, textphone in Europe, and minicom in the United Kingdom, is heavily used by those with hearing or speech impairments.The teletype was based on the Baudot Distributor, an automatic telegraph system that involved pairs of synchronized electromechanical machines. Both the Baudot Distributor and the teletype used the five-bit Baudot coding scheme. See also Baudot code, telegraph, and telex.