Abstract: A waveform equalizer for processing a signal read by a magnetic head from a magnetic written medium includes a slimming circuit which, in turn, has a first delay unit for delaying the read signal, a first attenuator connected in parallel with the first delay unit, a first differentiating circuit for receiving the output from the first delay unit and the output from the first attenuator, and a resistor connected to a first delay unit side input of the first differential circuit; and a pseudo-peak elimination circuit connected in series with the slimming circuit and including a circuit for separating the from the read signal the read signal or a signal reverse in phase to the read signal, a second delay unit for delaying the separated signal, a second attenuator for attenuating the amplitude of the separated signal, and a second differential circuit for receiving the read signal and the separated, delayed and attenuated signal.

Abstract: An error correction circuit which includes a specification circuit for specifying erroneous portions in a first data set reproduced from a recording medium, a register for storing the reproduced first data set including the erroneous portions thus specified and a reproducing circuit responsive to the reproduced first data set for reproducing again the first data set from the recording medium to obtain retry data, when there exist erroneous portions in the reproduced first data set stored in the register. The correction circuit also includes a data replace circuit, connected to receive the retry data, for replacing information at the specified erroneous portions in the reproduced first data set stored in the register by information at corresponding portions in the retry data.

Abstract: The time interval/amplitude level difference between sequential peaks in waveforms of first reproducing signals from a recording medium is detected and stored in a storage. The time interval/amplitude level difference between peaks in a waveform of a second reproducing signal from the recording medium is detected and compared with the time interval/amplitude level difference stored in the storage to thereby perform peak detection in the waveforms thereof. An original bit train of the first reproducing signal corresponding to a maximum-likelihood waveform selected among the waveforms of the first reproducing signals is given as a standardized signal. Data are provided to represent the time interval/amplitude level difference between the sequential peaks in the waveforms of the reproducing signals in a range of electromagnetic signal interference on the recording medium.

Abstract: A constant-density type of magnetic disk apparatus is made up of a plurality of magnetic disks, wherein at least one of the surfaces of the magnetic disks is a servo face divided into a plurality of zones in the radial direction of the disks. A magnetic disk used in this apparatus and a servo-writing device for making this magnetic disk are also disclosed. In the magnetic disk apparatus and the magnetic disk, servo information regions and clock information regions are alternately provided on the servo face in the circumferential direction of the disks. The servo information regions are arranged radially with respect to the rotation center of the disks and each of the clock information regions includes a plurality of magnetic transitions representative of clocks, the number of which is different for each of the divided zones.

Abstract: A disk drive unit is disclosed, which comprises a recording medium having more than two disk-shaped recording faces disposed on each other with an interval; information tracks disposed along the periphery on the more than two recording faces and servo signal fields on the recording faces, in the peripheral direction for different recording faces; more than two heads reading out servo information from the servo signal fields on the more than two recording faces; head moving means for moving the heads in the radial direction of the recording faces, linked with each other; means for obtaining position signals on the recording faces at different points of time for different heads on the basis of the servo signals; means for obtaining information on the relative velocity of the heads to the recording faces from the position signals at different points of time for different recording faces, and control means for effecting the velocity control by means of the head moving means on the basis of the information on the

Abstract: This invention provides a magnetic disk device having a total memory capacity of 30 giga bytes or more, or more desirably 30.about.40 giga bytes. The magnetic disk used in this magnetic disk device has a plane record density of 45.about.80 mega bits per square inch. The thin film magnetic head has a pole thickness (P.sub.T), a magnetic flux density (B.sub.s), a magnetic gap depth (G.sub.d) and a record wavelenth (.lambda.) which satisfy the formulaG.sub.d .ltoreq.0.13 P.sub.T B.sub.s (.lambda.+4.3)-2.1.The magnetic disk rotation means rotate the magnetic disk at a speed of 24 m per second or more.

Abstract: A readout circuit in magnetic recording device is disclosed, in which a test data signal for detecting an error in the characteristics of an automatic equalizer is recorded in a predetermined position of each track of a magnetic recording medium. In readout mode, a test data signal for a selected track is read out first, and this signal is compared with a reference signal dependent on the system conditions to determine an error from the reference signal. The optimum equalization coefficient is determined to eliminate this error from the reference signal and set in the equalizer. The data is readout under the optimum equalization characteristics thus set.

Abstract: A readout circuit in magnetic recording device is disclosed, in which a test data signal for detecting an error in the characteristics of an automatic equalizer is recorded in a predetermined position of each track of a magnetic recording medium. In readout mode, a test data signal for a selected track is read out first, and this signal is compared with a reference signal dependent on the system conditions to determine an error from the reference signal. The optimum equalization coefficient is determined to eliminate this error from the reference signal and is set in the equalizer. The data is readout under the optimum equalization characteristics thus set.

Abstract: In a magnetic disk drive apparatus having a plurality of actuators, or a magnetic disk drive system constructed of a plurality of head disk assemblies (HDA's); a magnetic disk drive apparatus or system in which the actuators included in the above apparatus or system can be arbitrarily and selectively coupled with a plurality of access control circuits and high power amplifiers that are smaller in number than the actuators.

Abstract: A signal read out circuit included in a magnetic recording device is disclosed in which plural kinds of slice levels are used simultaneously for a reproduced analog waveform to produce a plurality of gate signals corresponding to the slice levels, and it is judged on the basis of the gate signals whether each portion of the reproduced waveform is correct or not in producing a digital output.

Abstract: Disclosed is a magnetic recording medium of the magnetic metal thin-film type for longitudinal recording, in which the noise is reduced by selecting the value of maximum torque L (the product of magnetic anisotropy energy Ku and magnetic layer volume v; as measured by setting the axis of rotation in plane of the medium) and the value of magnetic flux .phi. (the product of saturation magnetization Ms and magnetic layer volume v) from a range defined by 0<L/(2.pi..multidot..phi..sup.2)<4.times.10.sup.5 (erg/emu.sup.2).

Abstract: A magnetic head for reading-out information magnetically recorded on a magnetic recording medium in a waveform varying between two different phases. The magnetic head includes at least one block of high magnetic permeability disposed adjacent to and directly facing a surface of the magnetic recording medium to be read-out so as to provide a magnetic path for passing therethrough magnetic flux emanating from the magnetic record on the magnetic recording medium. A magnetic material member is disposed adjacent to the at least one block so as to cause the magnetic flux emanating from the magnetic record on the magnetic recording medium to pass therethrough and is responsive to transition of the magnetic flux corresponding to variation from one phase to another phase in the waveform representing the recorded information so as to provide a predetermined physical effect. Further, a detecting arrangement is provided for the detecting the predetermined physical effect.

Abstract: In a read channel for magnetic recording used to reproduce information recorded on a magnetic recording medium, a signal reproduced from a magnetic head and a differentiated signal of the reproduction signal are ORed together to produce a gate signal. By using the gate signal, the information can be reproduced correctly.

Abstract: In a waveform processing circuit comprising a delay line for delaying a signal outputted from a ring type magnetic head reproducing a perpendicular magnetization recording, an attenuator for attenuating the signal delivered out of the ring type magnetic head, and a differential amplifier for receiving outputs from the delay line and the attenuator, wherein a waveform of the signal is processed to discriminate a position of magnetization transition based on the waveform of the signal; the delay time .tau. of the delay line is selected to satisfyv.multidot..tau..ltoreq.gwhere, v is a relative speed between the recording medium and the magnetic head and g indicates the gap length of the magnetic head.

Abstract: A waveform equalizing circuit including a delay line, an attenuator, and a differential amplifier applied with the outputs of the delay line and attenuator is disclosed in which the delay time of the delay line and the attenuation factor of the attenuator are changed in accordance with the characteristic of a waveform applied to the delay line and attenuator.

Abstract: An equalizer equalizes a reproduced waveform reproduced by a thin film magnetic head by reproducing information recorded magnetically on a medium. In the equalizer, the reproduced waveform is delayed to a position of an undershot portion, and is attenuated to an amplitude corresponding to a magnitude of the undershot portion, and the resultant waveform is superposed on the reproduced waveform, to thereby eliminate the undershot portion. Furthermore, by superposing a waveform obtained by inverting the reproduced waveform and amplifying or attenuating the inverted waveform, on the reproduced waveform at a half power position thereof, the width is narrowed.

Abstract: A current drive circuit for an induction coil is provided comprising a clamp circuit connected to the two terminals of the coil. This clamp circuit prevents the voltages of the two terminals from dropping below a reference voltage, thereby preventing decreases of the amplifier constants h.sub.FE of the transistors which are also coupled to the two terminals for a read-out operation.