Burroughs, Inc.

Xebec Development Partners, Ltd.

Norman S Blessum

Herbert U Ragle

Wilfred D Iwan

Michael Isaac Behr

Dean L DeMoss

Ko Ko Gyi

A disk drive control system including servo sectors written on a disk, with each sector containing three sets of marker pulses arranged so that three adjacent marker pulses from each of the sets spans two tracks. The pulses each comprise high frequency sinusoidal signals. Servo control depends upon the pulse amplitudes sensed by the read/write head while traversing a servo sector. The system includes an amplifier to rectify and amplify the high frequency signals, a sample-and-hold circuit to hold at least three value representative of the amplified high frequency signals, and synchronizing means to synchronize the sample-and-hold circuit such that the first value sampled and held is representative of the amplitude of the first pulse read in a servo sector, the second value sampled and held is representative of the amplitude of the second pulse read in the servo sector, and so forth. A multiplexing circuit provides multiplexed signals sequentially representative of values sampled.

Detection and amplification circuit

Techniques and associated apparatus for a magnetic disk transducing system adapted to record along spiral tracks in a Herringbone pattern, using a pair of orthogonal skew gaps, operating in tandem.

Spiral recording and associated system

Techniques and associated apparatus for a magnetic disk transducing system adapted to record along spiral tracks in a Herringbone pattern, using a pair of orthogonal skew gaps, operating in tandem. In a preferred embodiment, a pair of commonly mounted heads contemporaneously transduce along two respective spiral oppositely-skewed tracks separated by three (3) track widths.

Dual-track spiral recording and associated system

Improved disk drive equipment is illustrated, being characterized by improved partitioning means for partitioning a pack of flexible magnetic recording disks, the partitioning means featuring 'pneumatic commutator' means for distributing air streams to various inter-disk gaps in the pack--this commutator means constituting part of an external, rotationally stabilized jet-select apparatus.

Pneumatic commutator for end-wise partitioning

Techniques and associated apparatus for recording and detecting data; and especially for detecting and processing recorded data with greater accuracy. Recording information (computer data bits) is recorded in 'A-form' or 'B-form' as oblique parallel marks along adjacent information strips (tracks) on a medium, using a 'di-gap' transducer system comprising at least one related pair of transducer gaps aligned to register and sense information along a common record track, with the gaps being skewed oblique to the track direction, and aligned transverse to one another to register with respective A-form or B-form marks. One form of mark is preferably recorded along the ODD-number tracks, at a first frequency (f.sub.1) while the other form of mark is recorded along the EVEN-number tracks at a second, different frequency (f.sub.2). Output detect means are arranged to distinguish between these frequencies for improved recording (--e.g., head-position-servo control).

Di-gap, variable-frequency recording technique and associated system

Techniques and associated apparatus for positioning a magnetic transducer system relative to a selected recording track on a magnetic recording disk. Record information (computer data bits) is recorded along one or more information zones (tracks) of the disk and head-positioning information is derived from this according to a novel 'track-on-data' scheme. This scheme uses a 'di-gap' transducer system comprising at least one related pair of transducer gaps aligned to register and sense information along a common record track, with the gaps being skewed oblique to the track direction, and aligned transverse to one another. 'Servo-bits' (providing head positioning information) and 'work-bits' may both be recorded along a given track, these bits, like the mentioned gaps, being skewed relative to the track direction and aligned transverse to one another; the servo-bits in any one track thus being aligned parallel to one of the gaps while the companion work-bits are parallel to the other gap -- these gaps however being functionally interchangeable, with neither gap being dedicated to servo data or work data. Thus, once the di-gap head is moved along a given track, one gap will be aligned with the servo-bits and the other with the work-bits -- the two gaps being adapted to generate respective servo signals and data signals, the servo signal values (phase) automatically indicating the degree of head registration. Preferably, a related data encoding scheme establishes, for each track, the orientation of work-bits and servo-bits.

Track-on-data technique and associated system involving di-bit recording

Method and apparatus for providing coarse and fine radial positioning of a multiple head assembly relative to the concentric tracks of a rotatable magnetic disk. In addition to a plurality of data heads, the head assembly also includes a pair of position sensing heads having skewed core gaps disposed at an angle with respect to each other. These position sensing heads are used for prerecording concentric position control tracks on the disk as well as for subsequent sensing of position control information during both coarse and fine positioning operations. The position control information prerecorded in the position control tracks is specially chosen so as to provide a pair of pulse trains during position sensing having characteristics such that highly accurate and reliable control of head position can be achieved based upon a detection of the coincidence relationship between predetermined pulses of the respective pulse trains.

Transducer positioning system

Techniques and associated apparatus for recording and detecting data; and especially for detecting and processing recorded data with greater accuracy. Record information (computer data bits) is recorded along one or more information zones (tracks) of a medium. Head-positioning information may be derived from this, using a 'di-gap' transducer system comprising at least one related pair of transducer gaps aligned to register and sense information along a common record track, with the gaps being skewed oblique to the track direction, and aligned transverse to one another. 'Servo-bits' (providing head positioning information) and 'work-bits' may both be recorded along a given track, these bits, like the mentioned gaps, being skewed relative to the track direction and aligned transverse to one another; the servo-bits in any one track thus being aligned parallel to one of the gaps while the companion work-bits are parallel to the other gap, -- these gaps however being functionally interchangeable, with neither gap being dedicated to servo data or work data. Di-bits may be recorded (or pairs of parallel bits) in adjacent tracks but distinguished by recorded-frequency. Also, data read-out may be 'clocked' using means adaptive to varying data rate.

Di-bit recording technique and associated system

Data is recorded on a magnetic recording disk with data transducers adjustably positioned relative to a data zone. First and second control tracks are interspersed with the data zone in a parallel relationship. Positioned over each control track is a position sensing transducer mechanically linked to the data transducers. The control transducers each comprise core gaps used both for prerecording and subsequent reading of a position control pattern along their respective tracks. The core gaps extend diagonally at a predetermined angle to the direction of movement of the medium and provide control patterns defining multiple transition groups, the number of transitions related to a corresponding number of data tracks to be read by the data transducers. Positioning of the position sensing transducers is accomplished by measuring the time relationship between the output pulses of the two control tracks and by relating the resulting time differential to the radial distance over which the control head is to be actuated.

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Thousand Oaks, CA, United States of America

Norman S Blessum