A teleprinter (teletypewriter, teletype or TTY) is an electromechanical device that can be used to send and receive typed messages through various communications channels, in both point-to-point and point-to-multipoint configurations. Initially they were used in telegraphy, which developed in the late 1830s and 1840s as the first use of electrical engineering, though …

The Hellschreiber, Feldhellschreiber or Typenbildfeldfernschreiber (also Hell-Schreiber named after its inventor Rudolf Hell) is a facsimile-based teleprinter invented by Rudolf Hell.Compared to contemporary teleprinters that were based on typewriter systems and were mechanically complex and expensive, the Hellschreiber was much simpler and more robust, with far fewer moving …

Purpose and origins. Regular radio transmissions of "Tunny" messages started in June 1941. The British codebreakers saw that it used a five-unit code like a teleprinter system. Their research also showed that the coding was being done by a rotor cipher machine with 12 wheels (rotors). For each new message sent, the wheels had first to be turned to new positions.