A demodulation circuit includes a slope detector circuit and a comparator circuit. The slope detector circuit is configured detect a change in the voltage and determine if the voltage rate of change meets or exceeds one of a rise threshold or a fall threshold. The comparator circuit is configured to set an upper limit and lower limit for rate of change, compare the voltage rate of change to the limits, determine that the voltage rate of change meets or exceeds the limits, if the voltage rate of change meets or exceeds the rising and falling rate of change limits, (v) set a lower limit for a falling rate of change, (vi) receive the voltage rate of change and determine that the voltage rate of change meets or exceeds the fall or rise threshold, if the voltage rate of change meets or exceeds the falling or rising rate of change.