Abstract: A method of associating data with a plurality of heads in a disc drive apparatus employs heads disposed in physical locations in a head array. A plurality of data sets are provided, wherein each data set is associated with an address corresponding to the physical location of a respective head in the head array. In addition, the number of heads in the disc drive apparatus is determined and, based on the number of heads, a new head location scheme is selected. The new head location scheme defines a new head location for each physical head location address. Each data set is then associated with the new head location associated, in the new head location scheme, with the physical head location address associated with the data set.

Abstract: A disc drive includes a transducer having a separate element for writing information and a separate element for reading information to and from the disc. In a disc drive designated to read and write long sequential records, the track misregistration budget is reduced to account for previously written tracks not being encroached on one side. An initial track is written. Subsequent tracks are written after a seek in one direction. The subsequent track is written so that the initially written track is overwritten to one side and leaves a track having a width substantially equal to the width of the read element. Records can be written into data bands of a selected number of tracks. A guard band is left between groups of data bands so that data on tracks in subsequent data bands are not overwritten.

Abstract: A system and method are disclosed to facilitate independent positioning of a plurality of heads relative to associated disk surfaces in a disk drive system. Circuitry is provided to route position data from at least one of the heads while concurrently reading data from or writing data to another head. The position data is employed to control the position of the heads, each of which may be independently positioned by an associated positioning motor. Servo wedges associated with each surface also may be offset from each other to facilitate acquiring position data from one or more heads while data is concurrently communicated relative another head.

Abstract: A data storage system and device is provided in which parasitic capacitance between multiple preamplifiers and a signal channel is minimized. Multiple read signals from multiple data heads are amplified by corresponding ones of the multiple preamplifiers. A connection device coupled to each of the multiple preamplifiers selectively electrically couples the amplified read signal from the active preamplifier to the signal channel, while electrically isolating the amplified read signals from the inactive preamplifiers from the signal channel. In addition, a method of coupling multiple preamplifiers to a signal channel is provided.

Abstract: Apparatus and method for a head switching operation utilizing an automatic dummy load in a disc drive. A preamplifier circuit sequentially selects head positions and applies corresponding bias currents. A sequence control circuit automatically diverts the path of a first bias current from a head selection circuit to a dummy load after detecting an input of a second head location value into a buffer, and before the input is complete. After a bias current value for the second head is written into the buffer, the sequence control automatically deasserts the path to the dummy load after a predetermined time interval. The second bias current is then applied to the second head.

Abstract: An apparatus and method for extending the service life of an MR element incorporated in a read/write head involves detecting periods of disk drive system inactivity and selectively switching between the heads for purposes of reading servo information during the inactive periods. Switching between heads may involve selecting each of the heads for reading servo information during one or more periods of disk drive system inactivity or selecting each of the heads in sequence during a respective period of system inactivity. Selecting between heads may also involve selecting a head having a minimum of usage, such as a head having an MR element with a minimum of cumulative operational time or energy dissipation relative to other MR elements provided in the disk drive system. Selecting between heads may further include selectively activating each of the heads for reading servo information for a predetermined duration of time during one or more periods of system idleness.

Abstract: A disc drive with an information portion previously written on a rotatable disc surface, a servo write clock generator phase lock loop circuit controlling timing for writing a reference mark to the rotatable disc surface in substantial time alignment and phase and frequency coherent with the information portion previously written to the rotatable disc surface, a servo write clock generator phase lock loop circuit controlling timing for writing the reference mark, a pulse detector circuit for creating logic level signals from the reference mark, a pattern generator for generating reference mark write signals from the logic level signals, a memory buffer for storing radial position correction tables and values for writing the reference mark, and a self-servo control and sequencing circuit synchronizing timing signals for writing the reference mark to rotatable disc surface of disc drive.

Abstract: A recording disk apparatus is provided. The recording disk apparatus includes a recording disk having at least one recording surface with a plurality of spaced recording tracks. The recording disk also includes a positioning arm with a head assembly. The head assembly has a plurality of read transducers. Each consecutive transducer is positioned relative to one another at a distance substantially smaller than a spacing between two consecutive tracks.

Abstract: Apparatus and method for simultaneously biasing multiple magneto-resistive read elements in a disc drive head/disc assembly. A preamplifier circuit sequentially applies read bias currents to successive pairs of heads of the head/disc assembly, wherein the read bias current applied to a selected one of each pair of the heads is used to transduce the servo data from the associated disc recording surface, and the read bias current applied to the remaining one of each pair of the heads is used to prepare the remaining one of each pair of the heads to subsequently transduce the servo data from the associated disc recording surface. The preamplifier circuit includes at least first and second read bias current sources and a head selection circuit.

Abstract: A recording apparatus includes a thin film magnetic head (20) with eight write units (21-28) positioned adjacent to each other in a transversal direction (y) to write data in parallel tracks on a magnetic tape (10). Switching arrangement 70 has a switch (SW) to switch from a normal mode to a combination mode. In the normal mode the switch is in a first position (D1) and the switching arrangement (70) couple a first data signal (S1) to a first write unit (21), a second data signal (S2) to a second write unit (22) etc., so that in the normal mode eight tracks (T21-T28) are written on the tape resulting in a first track density. In the combination mode the switch is in a second position (D2) and the switching arrangement couples the first data signal (S1) to the first and second write units (21 and 22), the second data signal (S2) to the third and fourth write units (23 and 24) etc.

Abstract: A tape recording and playback unit records and reads back data from tape either in a high track density standard format or alternatively reads back data from a tape previously recorded on another unit in accordance with a previous low density standard track format. The unit includes a primary head positioning mechanism for positioning a primary multi-channel write/read head and a secondary head positioning mechanism for positioning a secondary read-only head. The secondary head may be positioned angularly to read longitudinal and azimuth track patterns, and also to be retracted when not needed.

Abstract: A read/write preamplifier circuit is provided that includes a fault detecting circuit that detects when two or more read/write preamplifiers are concurrently selected for communicating with their associated data heads and means for notifying the drive controller of that condition. In one embodiment of the invention, the means for notifying the drive controller that two or more preamplifiers are concurrently selected includes a data storage register that is readable by the drive controller and that has a fault flag which is set when two or more preamplifiers are concurrently selected. Also, in one embodiment, the fault detecting circuit includes a fault-detect transistor that drives a predetermined current if the preamplifier is elected. The collectors of the fault-detect transistors of each preamplifier are electronically coupled to each other and to a sensing circuit that senses if the fault-detect transistors of two or more preamplifiers are concurrently driving the predetermined current.

Abstract: A method for eliminating a wiggle of a magnetic head in a hard disk drive includes the steps of moving a first magnetic head to a parking area when wiggle is generated in the first magnetic head being in use, checking whether the first magnetic head is positioned in the parking area, using a second magnetic head at which the wiggle is not generated, and eliminating the wiggle by supplying current to the first magnetic head. The eliminating step further includes the step of supplying current to allow the first magnetic head to move to the parking area.

Abstract: This invention relates to head position control method for a disk device the uses a disk medium whose tracks have been formatted externally, and the disk device that effectively uses the range of motion of an actuator. In a disk device that has a disk medium (2), head (3), actuator (5), a control circuit (8), there is a conversion mechanism (31) that sets a data area in the writing range of the disk (2) that corresponds to the range of motion of the actuator, and converts a logical address to a physical address in the data area. This invention makes it possible to set a storage capacity that makes maximum use of the range of motion of the actuator for any device, even when there is position offset in the range of motion of the actuator.

Abstract: In a disk drive having a dual stage actuator, a method to improve head switching time by aligning a target head with a target track before a head switch occurs by using a second stage actuator attached to the target head to align the target head with the new track. The radial offset required to align the target head with the target track is either calibrated at startup or is measured dynamically during normal disk operations. A dual stage actuator with either a milli-actuator second stage or a micro-actuator second stage, positions a read/write head over a disk surface. The disk drive has a radial offset table for storage of radial offsets for head switches.

Abstract: In a head positioning method and device in which the position of position signals between heads is not uniform, it is aimed to reduce the time taken to find the position signals even when heads are switched. The storage disk device comprises a storage disk 1 with the position signal, a plurality of heads 3a through 3d that read the information from recording disk 1, an actuator 5 that moves the heads, and a control circuit 11 that positions the heads based on the position signals read from the recording disk by the selected head. This control circuit 11 comprises a synchronization circuit 6 that, in response to a head switching cue, synchronizes the time of the detection signal for detecting the position signal with the time of the position signal read by the head to which switching is directed, and a processing circuit 11 that reads the position signal for the head in response to the synchronized detection signal and positions the head in response to the position signal read.

Abstract: Proper coverage of data tracks of a magnetic tape in a magnetic tape drive is ensured by providing a head assembly having a set of read heads configured such that at least one of the read heads reads a desired data track as the magnetic tape moves across the head assembly. At least one of the read heads reads the desired data track by creating lateral differential motion of the head assembly with respect to the longitudinally extending data tracks of the magnetic tape. The differential motion is either created by tracking irregularities between the head assembly and the magnetic tape or by dithering or wobbling the head assembly with respect to the magnetic tape. In operation, a controller selects one of the read data signals generated by the read heads to generate a read back signal. The read back signal is the read data signal from the at least one of the two read heads reading the desired data track.

Abstract: Apparatus and method for simultaneously biasing multiple magneto-resistive read elements in a disc drive head/disc assembly. A preamplifier circuit sequentially applies read bias currents to successive pairs of heads of the head/disc assembly, wherein the read bias current applied to a selected one of each pair of the heads is used to transduce the servo data from the associated disc recording surface, and the read bias current applied to the remaining one of each pair of the heads is used to prepare the remaining one of each pair of the heads to subsequently transduce the servo data from the associated disc recording surface. The preamplifier circuit includes at least first and second read bias current sources and a head selection circuit.

Abstract: A recording disk apparatus is provided. The recording disk apparatus includes a recording disk having at least one recording surface with a plurality of spaced recording tracks. The recording disk also includes a positioning arm with a head assembly. The head assembly has a plurality of read transducers. Each consecutive transducer is positioned relative to one another at a distance substantially smaller than a spacing between two consecutive tracks.

Abstract: A data storage apparatus is provided in which the multiple disc surfaces for a disc stack are divided into multiple rotationally spaced apart servo frames. Servo data is written on the multiple disc surfaces within radially extending servo spokes such that each disc surface includes one servo spoke within each servo frame. Within each particular servo frame the servo spokes on each of the multiple disc surfaces are offset rotationally from one another. In addition, servo control circuitry and a method of using the same to provide positional reference signals for the staggered servo format are disclosed.

Abstract: A memory unit having a plurality of heads performing at least one of recording or reproducing operations on a storage medium is disclosed. The memory unit includes a first converter circuit for receiving head-selection signals as first parallel data and converting the head-selection signals to first serial data to be transmitted, and a second converter circuit for receiving the first serial data from the first converter circuit and converting the first serial data to second parallel data to be transmitted. The memory unit further includes a head control circuit for receiving the second parallel data from the second converter circuit and selectively driving the heads on the basis of the second parallel data.

Abstract: A tape recording and playback unit records and reads back data from tape either in a high track density standard format or alternatively reads back data from a tape previously recorded on another unit in accordance with a previous low density standard track format. The unit includes a primary head positioning mechanism for positioning a primary multi-channel write/read head and a secondary head positioning mechanism for positioning a secondary read-only head. The secondary head may be positioned angularly to read longitudinal and azimuth track patterns, and also to be retracted when not needed.

Abstract: A disk drive processing system controls a Servo Timing Mark (STM) detection window in disk drive during a head switch operation. In response to the head switch operation, the system disables a timer that closes the STM detection window during normal operation, and the system tracks the elapsed time from a time point. The system compares the elapsed time to a programmable limit value. The system resumes normal operation if an STM is detected before the elapsed time reaches the programmable limit value and initiates a recovery procedure if the elapsed time reaches the programmable limit value. Advantageously, the programmable limit value can be easily re-programmed if a larger STM detection window is required due to severe STM or head mis-alignment.

Abstract: A method and apparatus for performing head switch operations in a magnetic disk system having a magnetic disk device that is segmented into a plurality of cylinders, which cylinders are grouped into an inner zone, a middle zone, and an outer zone. The inner zone is near the innermost area of the magnetic disk device. The outer zone is near the outermost area of the magnetic disk device. The middle zone is in between the inner zone and the outer zone. The head switch is performed from a current head to a target head. Prior to the head switch, the system determines if the current cylinder is in either the inner zone or the outer zone. When the current cylinder is in either the inner zone or the outer zone, the system seeks the current head to the middle zone, whereupon the system performs a head switch from the current head to the target head. When the current cylinder is not found to be in either the inner zone or the outer zone, i.e.

Abstract: An apparatus and method are disclosed for minimizing damage to a disc drive during head switching operations. The disc drive comprises a plurality of magnetic recording surfaces to and from which data are transferred using read/write heads, each head utilizing the application of a bias current during operation. To switch from a presently selected head to a target head, the disc drive determines a first value indicative of the magnitude of a bias current for the presently selected head and a target bias current to be applied to the target head. When the second value is greater than the first value, the disc drive switches from the presently selected head to the target head and then applies the target bias current; conversely, when the first value is greater than the second value, the target bias current is applied to the presently selected head and then the disc drive switches from the presently selected head to the target head.

Abstract: A sector address recognition part recognizes a sector address in a magnetic disk where ID areas for storing sector address information and head address information are omitted. This is accomplished by generating a sector pulse when a predetermined count is reached after a detection of a servo mark and when an interval between adjacent servo marks included in servo information that also includes cylinder address information is a preset interval. A head identifier recognition part recognizes a head identifier on the basis of, for example, positions at which the servo information is recorded.

Abstract: A disk drive having an improved method of adjusting the head switch time to improve disk drive performance. In the process of writing or reading long data files, the heads on the actuator are sequentially selected in order to access all the data tracks forming a cylinder in the shortest time. Head offsets are significantly smaller for switching between heads mounted on the same actuator arm than for switching between heads mounted on different actuator arms. Therefore improved disk drive performance is obtained by using two values of head switch time instead of one. The head switch time allocated for switching from a first head on one actuator arm to a second head on a second actuator arm is made longer than the head switch time allocated for switching from a first head on one actuator arm to a second head on the same actuator arm. By allocating longer time for the head switches between different actuator arms, the error flag rate for heads not ready is reduced.

Abstract: A multi-head, disc drive, of a data storage system having a preamplifier that is split into a mother chip and set of daughter chips, each daughter chip corresponding to a head in the disc drive. The daughter chips contain very little circuitry, typically just a write driver, the front end of a read amplifier, a write fault detector, and a bias control circuit. Because the daughter chip contains little circuitry, it can be made much smaller and lighter than a conventional preamplifier, allowing the daughter chip to be placed on the suspension, close to the head. This allows the signal sent to and received from the head associated with a daughter chip to be strong enough not to be corrupted during transmission to the circuitry in the rest of the preamplifier. It also increases the bandwidth and reduces the power consumption of the preamplifier. The mother chip contains the remaining circuitry needed in the preamplifier and can be placed farther away, on a portion of the HSA that can support a larger chip.

Abstract: The system for gap positioning optimization in a tape drive takes advantage of the presence of a pair of read heads, located one on either side of the write head, to precisely determine the boundary between the inter-block gap and the data blocks adjoining the inter-block gap. In particular, the servo mechanisms in the tape drive note the location of the boundary between the present data block and the inter-block gap formed a the end of the present data block. When the tape is repositioned between data read/write operations, this servo information is used to identify this boundary to initiate the subsequently received data read/write operation. A predetermined amount of inter-block gap is provided at the end of the data block to ensure that subsequently received data is not written on top of the present data block or the overwriting of the next data record begins at the beginning of the data block.

Abstract: Read-while-write feedthrough is reduced in a tape deck having a multi-element read/write tape head. The tape deck includes write circuits for converting a substream of a data stream into an electrical signal. The read/write head has a sequence of write elements each having a coil for converting a received electrical signal into a magnetic field. A wire pair connects each write circuit with a corresponding write element. The system is designed such that the magnetization pattern written on the tape by one write element in response to a particular data substream has magnetization directions reversed from a second magnetization pattern written on the tape by a neighboring write element in response to the same substream. The feedthrough is thereby reduced by permitting cancellation of magnetic fields from write elements.

Abstract: A magnetic storage device for storing and retrieving data from a magnetic medium such as a magnetic tape. The magnetic storage device includes a first write gap, a first read gap and at least one of a second write gap and a second read gap with each gap operatively associated with the magnetic medium. A controller is coupled to each gap. The controller senses an error from a gap and stores an error flag.

Abstract: In a rotating magnetic disk storage device which uses an imbedded servo pattern for positioning an actuator, each transducer head comprises two magnetoresistive read elements, the read elements being separated by an insulating layer. The read elements are of different widths, the narrower element being used to read data, and the wider element being used to read servo patterns which locate the track centerline. The read elements are preferably deposited in layers on the rear of the slider body, with a thin-film inductive write head deposited in layers over the read elements. Preferably, the read elements are connected to three lead wires: a common ground lead, and separate sense leads. The sense amplification electronics alternatively sense resistance changes in one element or the other as the head passes over data or servo patterns. Because the narrow read element is used for reading data, noise due to reading too close to the edge of the track can be reduced.

Abstract: A method and apparatus for performing head switch operations in a magnetic disk system with a magnetic disk device that is segmented into a plurality of cylinders. The cylinders are grouped into an inner zone, a middle zone, and an outer zone. The inner zone is near the innermost area of the magnetic disk device. The outer zone is near the outermost area of the magnetic disk device. The middle zone is in between the inner zone and the outer zone. The head switch is performed from a current head at a current cylinder to a target head at a target cylinder. Prior to the head switch, the system determines if the current cylinder is in either the inner zone or the outer zone. If the current cylinder is in either the inner zone or the outer zone, then the system determines if the target cylinder is in either the inner zone or the outer zone. If the target cylinder is in either the inner zone or the outer zone, then the system seeks the current head to the middle zone and then performs the head switch.

Abstract: A head-switching circuit for switching a first head operating on a first recording medium to a second head operating on a second recording medium so as to read out data written on a recording medium according to a staggered servo mechanism, includes a selector for selecting one of the recording media, a classifier 20, 30, 31, 32 and 33 for classifying the skew time of a recording medium selected by the selector and another recording medium selected by the selector, a sync signal generator 40, 41, 42, 50, 51, 60, 61, 62, 70, 71, 72 and 80 enabled by the output signal of the classifier and for generating a sync signal when the skew time is identical with a predetermined time, thereby generating a sync signal precisely during head-switching in staggered servo mechanism.

Abstract: There is provided a magnetic tape drive capable of attaining a stable read-out output value of information even if a tracking displacement occurs. The magnetic tape drive of the present invention is a magnetic tape drive for 36-track comprising a magnetic tape 1a having a width of 1/2 inch and having information written therein by an 18-track magnetic tape drive, a plurality of magnetic heads 2, 3 for performing a reading of information of each of the tracks in the magnetic tape 1a and a control section 9 for controlling a writing or reading operation for information from the magnetic heads 2, 3, wherein as the magnetic heads, each of the forward reading head 2 and the reverse reading head 3 is installed in correspondence with each of the tracks of the magnetic tape 1a.

Abstract: An information recording/reproducing apparatus capable of correctly reproducing information from a large number of recording tracks without requiring tracking servo. A recording medium is formed with at least one pilot track on which a pilot signal is recorded and a plurality of information data tracks which have the same track width as the pilot track and on which information data is recorded, where the pilot track and the information data tracks are arranged adjacent to each other.

Abstract: A method formats disc surfaces in a disc drive for storage of data in a group of tracks on the disc surfaces. The disc drive performs seek operations to seek among cylinders on the disc surfaces as a function of time according to an actual seek profile. An approximation of the actual seek profile is determined such that the actual seek profile falls within the approximation. The disc surfaces are formatted according to the approximation of the actual seek profile.

Abstract: A storage device is described for reading data from a hard disk drive wherein delays due to rotational latency are substantially reduced. The storage device includes a platter having a substantially planar annular surface with a geometrical center. On the platter are a plurality of generally arcuate concentric tracks. Each of the tracks is divided into a plurality of sectors that are radially outwardly disposed from the geometrical center of the platter and are bounded by radii extending from the geometrical center. Original data is written on at least one of the sectors. Further, a copy of the original data is maintained at a fixed azimuth angle from the original data during rotation of the platter about the center.

Abstract: A system for providing feedback to a selected read head in a multi-head disk drive includes first and second feedback circuits is disclosed. A first feedback circuit 200 provides for correction of the output of the selected read head during normal operation. The first feedback circuit 200 produces a differential output current proportional to an offset voltage detected on the read head output nodes 103 and 104. This differential output current charges external capacitor 190. The voltage across capacitor 190 is supplied to voltage inputs of the selected read head as a feedback voltage. When the feedback voltage reaches the desired level, nodes 103 and is 104 equalize, as do the output currents of the first feedback circuit 200. The second feedback circuit 300 provides for quick recovery of the system after a change in read heads.

Abstract: An apparatus for recording information signals in a track (T.sub.i) on a record carrier (2) is disclosed, comprising an input terminal (30) for receiving an information signal, a signal processing unit (32) for processing the information signal so as to make the information signal suitable for recording in at least one track on said record carrier, and a writing unit (33) for writing, after processing, the information signal in said at least one track on said record carrier, starting from a start position (s) viewed in the length direction of the record carrier and in a direction towards one of the end positions of the record carrier.The portion of the record carrier (2) between said start position (s) and said one end position (L.sub.2) is fictitiously divided into a first sub portion lying (P.sub.1) adjacent the start position and a second sub portion (P.sub.2) lying adjacent the end position of the record carrier.

Abstract: On an FCP board and in a head amplifier circuit, provided for amplifying a read signal from a head and supplying the read signal to a read channel, a dummy wiring pattern is located near a wiring pattern for supplying the read signal. The head amplifier circuit incorporates a differential amplifier. The differential amplifier finds and amplifies a difference between the read signal supplied through the wiring pattern and the noise signal supplied through the dummy wiring pattern. The differential amplifier outputs to a read channel the read signal from which the noise has been removed.

Abstract: A device for formatting a linear data storage tape includes a servo write head configured to write a pattern of magnetic transition stripes along a servo band of the linear data storage tape. The servo write head is configured to produce stripes having lateral widths that are significantly greater than that of a servo read element of a data read/write head designed for use with the linear data storage tape. Each stripe has either a positive non-zero azimuth or a negative non-zero azimuth. The device also includes a magnetic readback element that produces a servo verify signal. The magnetic readback element extends laterally across the full widths of the magnetic transition stripes and is oriented at an azimuth between the positive and negative non-zero azimuths of the magnetic transition stripes. A pulse detector is configured to detect pulses in the servo verify signal.

Abstract: A method and apparatus for optimizing the seek/settle performance of a storage device. The present invention measures the seek/settle performance for each individual head and selects the heads with the best seek/settle performance, i.e., access performance. The invention includes a processor for calculating velocity deviations for each of the plurality of heads to determine a set of suitable seek heads from the plurality of heads, a head selection circuit for switching from a current head to a preferred head from the set of suitable seek heads and an actuator controller for seeking with the preferred head to a virtual track corresponding to a target track. The processor calculates a preferred/target runout difference for smoothing the settle of the preferred head and the head selection circuit switches from the preferred head to a target head aligned with the target track.

Abstract: A switch device switchable as a first channel (200) to an inactive state and a dummy channel (201) to an active state the switching device switches the dummy channel to an inactive state while switching a second channel 300 to an active state.

Abstract: Tilt values between heads in a disk drive apparatus are previously measured. The measured values are stored in a head switch compensation table. In a head switch operation, a track nearest to the present position of a head to be used after a head switch operation is selected as a target track for the head to be used. A head switch compensation table is stored in a disk. The head switch compensation table stores tilt values represented by a number of tracks which corresponds to a relative deviation between heads. For example, if the table contains data showing that a tilt value between head 1 and head 2 is +1 track, then when heads are switched from head 1 to head 2, a target track for head 2 is selected by adding this value +1 to the current track address on which head 1 is positioned. By this method, head 2 can be positioned on the nearest track by a short time seek operation and can continue a sequential read or write operation.

Abstract: A method and system of magnetic recording of information elements on several parallel tracks whereby the recording of information elements on a track is accomplished by inducing a magnetic field having a predetermined direction in a zone on the track and, during this recording, inducing a magnetic field with a reverse direction in zones of the neighboring tracks. A winding (L0, L1, L2) of each head is coupled to at least two winding of neighboring heads. A control current transmitted to the head provides at least one current diverted towards the neighboring heads.

Abstract: A system for the reading of a multitrack recording medium comprising a device enabling the reading, on the width of each track, of a number n of information samples. The system includes a filter enabling the making of several combinations of several samples of a track, these combinations differing from one another by a shift equal to one or more samples; a sub-sampling circuit that chooses a determined combination from among the different combinations of a track under the control of a position predictor; a positional error computation circuit computing the positional error of the chosen combination and giving an error correction signal to the position predictor.

Abstract: For clock extraction (Cl.sub.n) from n digital signals read from each of n tracks (T.sub.a.1 to T.sub.a.n), there are provided n phase-locked loops (13,n). Voltage-controlled oscillator (21) is common to the n phase-locked loops. Each phase-locked loop further includes a phase-shifter unit (25.n) having an input coupled to the output of the voltage-controlled oscillator (21) and an output coupled to the second input of the phase comparator (17,n) in the loop. The phase shift in the phase-shifter unit (25.n) is controlled under the influence of a control signal which is derived by a control signal generator (26.n) and applied to a control signal input (29) of the phase-shifter unit (25.n). The control signal generator unit (26.n) is an integrating element.

Abstract: A switch is provided which successively switches contacts at a timing sufficiently quick with respect to reproduced signals in reproducing a magnetic tape on which digital recording is effected, and which switches contacts at similar timing in reproducing a magnetic tape on which analog recording is effected. On signals provided through this switch and through an analog-digital converting circuit, processing such as waveform equalization corresponding to the type of magnetic tape is effected by a digital equalizer. By this digital equalizer, correction of frequency characteristic in accordance with the type of the magnetic tape and correction of frequency characteristic inherent to the head per se are effected.

Abstract: A video time-shifting system characterized in having a continuous recording track accessed by separate, asychronous read and write facilities enables playback of a video program to commence from any point in the program while continuing to be recorded in real time, thus providing VCR-like program control features such as PAUSE/RESUME, REWIND, and FAST FORWARD. A memory is used to store information relating to various points in the program so that even upon receipt of multiple PAUSE commands, the system automatically keeps track of correct program re-entry. In the preferred embodiment, the storage means takes the form of a continuous recording track in a magnetic disk drive.