\*****************************************************************
\          BEAM BREAK DEFINED - 20ms BREAK, 20ms RELEASE
\*****************************************************************
S.S.2,  \ Beam Break Defined - 20ms Break, 20ms Release.
S1,     \ Inputs in Level Mode generate an input "count" on each
        \ interrupt.  With a 10 ms system resolution 2 counts
        \ will be reached in 20 ms.  The Z3 pulse is used to
        \ signal a completed Beam Break.  The second statement resets
        \ the counter every 20 ms so that a partial Beam Break of
        \ less than 20 ms will not constitute a Response.
  #R1: ADD Y; IF Y >= 2 [@BeamBreak, @NoBeamBreak]
                 @Break: Z3; SET Y = 0 ---> S2
                 @NoBreak: ---> SX
  0.02": SET Y = 0 ---> S1

S2,     \ As long as the Beam is broken the second statement
        \ causes a re-entry to this State.  This resets the
        \ the internal 20 ms timer so it never times out.  When
        \ the Beam is released for 20 ms the timer times out
        \ and a Z4 pulse signals the release.
  0.02": Z4 ---> S1
  #R1: ---> S2