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

encoder

   1.  Any program, circuit or algorithm
   which encodes.

   Example usages: "MPEG encoder", "NTSC encoder",
   "RealAudio encoder".

   2.  A sensor or transducer for converting rotary
   motion or position to a series of electronic pulses.

   (1997-03-04)