Duplex \Du"plex\, a. [L., fr. duo two + plicare to fold. See
   {Two}, and {Complex}.]
   1. Double; twofold.
      
[1913 Webster]


   2. (Computers) organized so that data may be transmitted in
      two opposite directions over the same channel; -- of
      communications channels, such as data transfer lines
      between computers.
      [PJC]

   {Duplex escapement}, a peculiar kind of watch escapement, in
      which the scape-wheel has two sets of teeth. See
      {Escapement}.

   {Duplex lathe}, one for turning off, screwing, and surfacing,
      by means of two cutting tools, on opposite sides of the
      piece operated upon.

   {Duplex pumping engine}, a steam pump in which two steam
      cylinders are placed side by side, one operating the
      valves of the other.

   {Duplex querela} [L., double complaint] (Eccl. Law), a
      complaint in the nature of an appeal from the ordinary to
      his immediate superior, as from a bishop to an archbishop.
      --Mozley & W.

   {Duplex telegraphy}, a system of telegraphy for sending two
      messages over the same wire simultaneously.

   {Duplex watch}, one with a duplex escapement.

   {half duplex} (Computers)
      (a) arranged so that the information may be transmitted in
          both directions, but only in one direction at a time;
          -- of communications channels between computers;
          contrasted with {full duplex(a)}.
      (b) arranged so that the information transmitted to the
          remote computer also appears on the local terminal; --
          of communications channels between computers;
          contrasted with {full duplex(b)}.

   {full duplex}, (Computers)
      (a) arranged so that the information may be transmitted in
          both directions simultaneously; -- of communications
          channels between computers; contrasted with {half
          duplex(a)}.
      (b) arranged so that the information transmitted to the
          remote computer does not appear on the local terminal;
          -- of communications channels between computers;
          contrasted with {half duplex(b)}.
          
[1913 Webster]