<CommuniCations> A term applied by Western Union Telegraph Company to teletypewriters that are not part of a multiplex system. They usually provided for alternate transmission in both direCtions. If working simplex or half-duplex, what was keyed in at the keyboard would be typed out at the printing portion. If working full-duplex, sending would be blind as the printing portion was being used only for reCeption. (2000-04-02)