Abstract: In an apparatus, for example, an 8-mm format VTR, for selectively reproducing video data and digital data, such as, PCM audio data, recorded on a magnetic medium with any one of a plurality of recording densities, the recording density of the digital data is detected on the basis of a characteristic of the reproduced digital data, such as, a characteristic clock frequency regenerated therefrom, and the processing to which the reproduced digital data is subjected is selected automatically in accordance with the detected recording density thereof, thereby facilitating the use of the apparatus for reproducing digital data recorded with different densities.

Abstract: In an apparatus for magnetically recording and/or reproducing digital signals in a plurality of modes characterized by different respective formats, pilot signals having different frequencies are generated to identify the modes, respectively, and, during a recording operation in one of such modes, the respective pilot signal is mixed with the digital signal to be recorded for providing a resultant mixed signal which is recorded. Thereafter, during a reproducing operation of the apparatus, the pilot signal included in the reproduced mixed signal is detected for determining the format of the recorded signal on the basis of the frequency of the detected pilot signal, whereupon the respective mode of the apparatus is established.

Abstract: Data reproducing apparatus for reproducing data that is recorded with a selected one of at least two different recording densities such that the played back data may exhibit different frequency characteristics, depending upon the recording density. The played back data is supplied to a selected one of plural equalizer circuits whose respective equalizing characteristics match the frequency characteristics of the played back data, thereby reducing the bit error rate of the played back data, regardless of the particular recording density with which that data had been recorded.

Abstract: In an apparatus for recording data on a magnetic recording medium by means of a magnetic head, a recording current supplied to such head, for example, from a recording amplifier, is varied in accordance with the recording density of the data being recorded so as to reduce the bit error rate upon playback or reproducing of the recorded data. For each recording density, the recording current supplied to the magnetic head is a predetermined amount greater than the optimal value of the recording current at a Nyquist frequency of the digital data being recorded.

Abstract: In an apparatus, such as, an 8-mm VTR, in which a pilot signal and a digital signal modulated by an information signal, and occupying frequency bands that overlap at least in part, are recorded together as an addition signal in a track on a recording medium; a D.C. component of the addition signal reproduced from the track is detected and compared, in a voltage comparator, with the level of the reproduced addition signal so as to provide the digital signal as an output of the comparator, and such output of the voltage comparator is subtracted from the reproduced addition signal so as to provide the pilot signal without error by reason of the digital signal. Further, the pilot signal and cross-talk from adjacent tracks obtained from the first-mentioned subtraction is, in turn, subtracted from the reproduced addition signal for obtaining the digital signal therefrom, and the D.C.

Abstract: In a digital data reproducing apparatus for demodulating digital data recorded on a magnetic medium with either a first or second record modulation mode, such mode is detected by identifying the frequency of a recovered clock signal derived from the digital data by a clock recovery circuit, and an appropriate demodulation circuit for the recording mode is then selected to demodulate the reproduced digital data.

Abstract: A clock regeneration circuit for use in data reproducing apparatus which reproduces and demodulates digital data that has been recorded on a magnetic medium in accordance with different types of modulation having different recording densities, such as biphase-mark modulation and 8-10 modulation, respectively. The clock regeneration circuit includes a phase locked loop for regenerating a clock signal from the clock component included in the reproduced data and comprises a switchable voltage controlled oscillator for selecting the frequency of a reference signal generated thereby in correspondence with the type of modulation which had been used for recording. Also included in the clock regeneration circuit is a phase comparator and a switchable low pass filter for supplying the output of the phase comparator to the voltage controlled oscillator, the time constant of the filter being selected in correspondence with the type of modulation that was used for recording.

Abstract: In tape transport apparatus for use with an 8-mm video tape recorder having an automatic track following system, during reproduction at a variable tape speed, a tracking error signal formed on the basis of a frequency component of a reproduced pilot signal is sampled and held once per one field. The sampled and held output is compared with a reference value, the running state of the tape is positively identified on the basis of the comparison, and tracking control responsive to the identified running state is carried out. The apparatus has the additional capability of skipping pilot signal frequencies in a quasi-locked state to assist in obtaining a locked state.