Source : Free On-Line Dictionary of Computing

set-top box
     
         (STB) Any electronic device
        designed to produce output on a conventional televesion set
        (on top of which it nominally sits) and connected to some
        other communications channels such as telephone, {ISDN},
        {optical fibre} or cable.  The STB usually runs software to
        allow the user to interact with the programmes shown on the
        television in some way.
     
        {Online Media} are one STB manufacturer.
     
        (1997-05-16)