[W/K] :: simplex

  simplex
       adj 1: allowing communication in only one direction at a time, or
              in telegraphy allowing only one message over a line at
              a time; "simplex system"
       2: having only one part or element; "a simplex word has no
          affixes and is not part of a compound--like `boy' compared
          with `boyish' or `house' compared with `houseboat'"

  simplex
       
          1.  Used to describe a communications channel
          that can only ever carry a signal in one direction, like a
          one-way street.  Television is an example of ({broadcast)
          simplex communication.
       
          Opposite: duplex.
       
          2.  The simplex method.
       
          (2001-07-21)
       
       

  SIMPLEX. Simple or single; as, charta simplex, is a deed-poll, of single 
  deed. Jacob's L. Dict. h.t.