Abstract: In a clock generator for magnetic disk drive of the zone-bit recording type in which a training signal is written in a preamble portion of data, comprising: a sample-holder circuit for generating a sampling signal from a read signal; a phase-comparator for detecting a phase difference from the sampling signal; a loop filter; and a voltage-controlled oscillator whose frequency is controlled by the phase difference as it is smoothed; there is provided a frequency divider; a clock extraction circuit for extracting a clock timing from the training signal as it is equalized partially-response signal; and a phase-comparator for finding a phase difference from an output of the frequency divider and an output of the clock extraction circuit, and the phase-comparator is connected to the loop filter during reproduction of the preamble portion of the data and the phase-comparator is connected to the loop filter during reproduction of a data portion of the data by the switching of a change-over switch.

Abstract: A pulse qualification apparatus and method provides for qualifying signal pulses from a raw data signal by comparison to a variable qualification level. Pulse qualification is done on a read signal developed by moving a magnetic transducer relative to addressable portions of a magnetic disk. A qualification level generator circuit generates a qualification level signal which varies in value depending upon the addressed portion of the magnetic disk. A threshold detector is used in qualifying pulses from a transducer read signal by comparison to the qualification level signal to generate an encoded pulse signal representing occurrences of qualifying pulses.

Abstract: A recording or reproducing of an input video signal is prohibited in a recording mode operation when a recording inhibition signal is attached thereto and, when a mode other than the recording mode is set, the video signal of optimum level can be supplied to a television receiver even if the recording inhibition signal is attached to the video signal so that a sufficient monitoring becomes possible.

Abstract: A recording device includes a first unit operable in response to head positioning information to generate a first positioning signal for positioning a head at a predetermined track and a second unit operable in response to the first positioning signal to generate a second positioning signal for positioning the head at either a track between adjacent predetermined tracks or a position correction information area which is offset from the data area, thereby providing a high density and high precision recording device.