Abstract: A circuit for reproducing and demodulating a modulated digital signal which is modulated in a predetermined modulation system such as MFM, EFM and so on. A phase of a clock having a frequency multiplied by an integral number of a bit frequency of the modulated digital signal, is restricted or controlled by a signal showing that a predetermined pattern of the modulated digital signal occurred. The modulated digital signal is demodulated by the thus restricted clock to produce digital informations "0" and "1". A main requirement for detecting the predetermined pattern of the modulated digital signal, is that a reproduced modulated digital signal is reliable. In order to compensate for the drop-out of the modulated digital signal, the demodulation circuit is provided with a modulated digital signal reproducing circuit for complementing a predetermined signal pattern when the drop-out occurred.

Abstract: A digital audio disc (DAD) reproducing apparatus comprises pulse width detection and pulse width-to-voltage conversion means for detecting a signal having a predetermined pulse width such as a maximum or minimum pulse width of code modulated digital data signals reproduced by a pickup and converting the detected signal to a voltage proportional to the pulse width, and pulse width error detection means for detecting an error between the converted voltage and a reference voltage corresponding to a reference pulse width. Since the pulse width of the digital data signal changes with a clock rate, the error from the reference voltage represents an error in the clock rate.

Abstract: A PCM recording system uses vertical and horizontal synchronizing signals like those of a television video signal, and records PCM sound signal data taking the form of PCM signals converted from a sound signal during specific ones of plural horizontal scanning periods disposed between the vertical synchronizing signals. At least one control signal such as an absolute address signal representing a tape position, an operation indicating signal for indicating the operations such as a tape running stop and a tape rewind and an adjusting signal for adjusting a reproducing system is recorded during the horizontal scanning period with no recording of the PCM sound signal data. At the time of signal reproducing, the control signal is extracted to perform a given display or a given control.

Abstract: There is disclosed a vertical synchronizing signal detector circuit for use with a PCM recording/reproducing system which records and reproduces audio signals with pulse code modulation by the use of a home VTR system or a part thereof.