To decode signals modulated in frequency or pulse width (PWM) the configuration used is the one shown in the figure. The central frequency of the carrier is set in P1 and the output has a signal whose amplitude depends on the frequency deviation of the input signal in relation to the frequency for which the PLL has been adjusted. This circuit can be used as a decoder for a communications system modulated via the power grid. The supply voltage must be between 5 and 10 V.
