Abstract: A track following positioning system including filtered average servo demodulators for maintaining the position of a magnetic tape head in alignment with tracks of data stored in magnetic medium. A servo head tracks a centerline in a servo written region of the magnetic medium and generates servo head signals corresponding to the displacement of the servo head from the centerline. A filtered average servo demodulator detects the servo head signals and generates servo error signals for realigning the tape head with respect to the magnetic medium in response thereto. To generate servo error signals, the filtered average servo demodulator peak detects and averages the rectified and filtered output signals and then subtracts a proportion of the peak detected signals from the average detected signals.

Abstract: A magnetic recording head positioning system includes a Terfenol-D magnetostrictive rod prestressed by a lever arm to operate in a linear range to microposition the magnetic recording head in accordance with an electromagnetic field. The mechanical advantage of the lever arm amplifies changes in the magnetostrictive rod to position the head. The varying electromagnetic field is applied to the rod by a coil in response to a position error signal produced from servo data tracks on the magnetic tape. A permanent magnet system biases the magnetostrictive element with a DC field so that varying the field provides bi-directional motion of the magnetic recording head. The DC field also reduces coil current and size requirements.

Abstract: In a magnetic storage system, an error recovery is performed by reading the magnetic medium again with the filter programmed to a higher boost. If the retry still fails, the magnetic medium is read again with the filter programmed to a lower boost. The filter adjustment can be performed in combination with position adjustment of the read head, i.e. displacing the read/write head from the centerline of the track during error recovery to reduce read errors.

Abstract: The present invention discloses a method and an apparatus for the detection and correction of incorrectly digitized read data pulses corresponding to the pulses of an analog read signal generated from the reading of data from a magnetic storage tape. Detection of incorrectly digitized read data pulses is performed by delaying the signal to obtain a nominal signal and delaying the nominal signal to obtain a late signal. A recovered clock signal is used to synchronize and detect each of the early, nominal and late signals to obtain early, nominal and late synchronized data signals consisting of binary values. A predetermined number of binary values of each of the synchronized data signals is stored within first, second and third memory means. These binary values are then compared to determine whether any of the corresponding read data pulses were detected within an incorrect timing cell of the recovered clock.

Abstract: A look ahead detector based on a delay line is used in a pulse amplitude qualifier circuit to qualify detected peaks in a system for the recovery of magnetically recorded digital information. The analog signal is delayed by one cell period to create a delayed replica which is applied to the peak detector. The difference between the analog signal and the delayed replica is applied to a hysteresis flip flop to create a qualifying signal based on a threshold value proportional to the analog signal to gate the peak detected in the delayed replica.

Abstract: An oscillating erase current circuit for erasing information recorded on magnetic media. The inductance of an erase head is coupled with capacitors to form a tank circuit having a natural resonant frequency. The self-oscillating erase current circuit generates an oscillating signal having a frequency of oscillation determined by and therefore equal to the natural resonant frequency of the tank circuit. Once enabled, the self-oscillating erase current circuit continuously oscillates without any external drive circuit.

Abstract: Special tape drive read circuitry generally qualifies read voltage peaks by establishing a minimum amplitude for valid peaks in the read voltage signal so that noise is not interpreted as peaks, but does not require amplitude qualification during periods of dropout in the read voltage signal. Additional circuitry recognizes two of the data errors most common to GCR, and allows for these errors to be corrected. The first kind of error is the tri-bit error, in which 01110 is misinterpreted as 01000. The other kind of error is the low frequency error, in which 10010 is misinterpreted as 11000. Also, the type of error detected is used to adjust the read drive's hysteresis setting, to reduce future errors of the same type.

Abstract: A closed loop resolution enhancement technique for reducing density effects to permit increased digital data storage density on magnetic media and improve data reliability for at a given density, uses a predetermined test pattern written on the medium to determine the ratio of amplitudes of high and low frequency components of the test pattern and adjust a resolution value. After a test pattern read operation is used to adjust the resolution value, the same value is used during normal data recovery operations.

Abstract: A cartridge tape drive having a housing with an opening dimensioned to allow endwise insertion of a rectangular cartridge with an access door along a side edge thereof. The cartridge is supported on a stationary support within the housing. The cartridge tape drive is provided with a mechanism which opens the access door, and a mechanism which moves the cartridge laterally within the housing into operative engagement with a magnetic head. The magnetic head is attached to the stationary support.

Abstract: A cartridge tape drive having a housing with an opening dimensioned to allow endwise insertion of a rectangular cartridge with an access door along a side edge thereof. The cartridge is supported on a stationary support within the housing. The cartridge tape drive is provided with a mechanism which opens the access door, and a mechanism which moves the cartridge laterally within the housing into operative engagement with a magnetic head. The magnetic head is attached to the stationary support.

Abstract: A system and method for slowing the data transfer rate in a magnetic tape cartridge drive is presented for a better match in transfer rates between a host computer and the drive. The transfer is slowed after the start of the data transfer operation to selected transfer rates below the nominal transfer rate of the drive. The requirements of density of data on the magnetic tape remains unaffected so that the magnetic tapes are interchangeable with present drives.

Abstract: A technique for operating a data storage medium, such as a magnetic tape cartridge, by writing pairs of buried servo data tracks having alternating flux densities. A servo read gap is used to locate the on-track position at the border between a pair of servo tracks by detecting a fixed relationship, such as a predetermined proportionality correction factor, between the signals read from each track. Information data read and write gaps are mounted to the servo read head to create a plurality of information data tracks, each one half or less the width of a servo data track or smaller and separated from the next track by one half the servo track width. Information data tracks are formed in these separations between tracks by positioning a second servo data read head at a distance equal to the width of an information data track pitch from the first servo read head while using the second servo read head to locate the on-track position.

Abstract: A stepper motor in a magnetic tape cartridge head positioning system applies vernier control to achieve a final target after a preliminary target has been achieved by stepping. The vernier control is provided by a closed loop servo system in which current is applied to stator coils selected so that the target is at a torque maximum rather than at a torque null. Current proportional to a servo error signal is applied to selected stator coils so that the torque is sufficiently linearly related to position to permit classical linear servo analysis for the design of a stable, non-oscillating system. An example of stator coil selection for advancing and retarding a permanent magnet stepper motor operated in eight half steps is provided below in Table 1.

Abstract: A cartridge tape drive having a housing with an opening dimensioned to allow endwise insertion of a rectangular cartridge with an access door along a side edge thereof. The cartridge is supported on a stationary support within the housing. The cartridge tape drive is provided with a mechanism which opens the access door, and a mechanism which moves the cartridge laterally within the housing into operative engagement with a magnetic head. The magnetic head is attached to the stationary support.