Crystal controlled frequency discriminator

Claim 1

Demodulating apparatus comprising: a register having a plurality of stages and responsive to a bifrequency modulated input signal for delaying its output signal for a fixed time interval, clock signal generating means coupled to said register for providing a signal that clocks said frequency modulated input signal through said register, said fixed time interval being determined by the number of stages of said register and the frequency of said clock signal, and gating means coupled to receive said modulated input signal and said delayed register output signal for producing an output signal having pulses of constant amplitude and duration with the duty cycle of said pulses being determined by the phase difference between said modulated input signal and said delayed register output signal, and circuit means coupled to said gating means for averaging out the output signal of said gating means and producing a bi-level signal which represents the bilevel modulation of said modulated input signal said circuit means further including means for squaring the bi-level signal to produce a second bi-level signal more suitable for application to a computer.