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   Computes the effective pulsewidth given the rise and fall times.
   If pulsewidth is not entered, it will use a range from 0.02 to 1 sec.
   If tauMax is not entered it will assume an infinite control period.
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   Form:
   effPw = EffPw( tauRise, tauFall, pulsewidth, tauMax )
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   ------
   Inputs
   ------
   tauRise          (1,1) Rise time constant
   tauFall          (1,1) Fall time constant
   pulsewidth       (1,:) Pulsewidths
   tauMax           (1,1) Control period

   -------
   Outputs
   -------
   effPw            (1,:) Effective pulsewidth

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