V.E.R.A. -- Virtual Entity of Relevant Acronyms (February 2016):

STB
       Software Technical Bulletin


The Free On-line Dictionary of Computing (30 December 2018):

set-top box
STB

    (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)