a demodulation system of a playback device for a carrier frequency signal containing both useful information in the zero passages of the signal and signal break - ins which occur in the playback device . the system includes a limiter for limiting in an asymmetrical manner a signal fed to it and a demodulator coupled to the output of the limiter . a highpass filter is connected between the limiter and the demodulator so as to couple the output signal from the limiter to the demodulator . the highpass filter substantially passes only the useful information portion of the carrier signal and suppresses any break - ins introduced into the signal .