Abstract: A method and apparatus for (1) reducing storage requirements by use of novel encoding/decoding lexicographically code and decode state-dependent codes, and (2) locally reordering coded subsequences to permit direct NRZ coding, which is especially desirable when using PRML sequence detection.

Abstract: A circuit for concurrently producing low noise electrical output signals which are amplified representations of signals produced by a magnetoresistive (MR) element and protecting said element from electrical short circuits which can occur between said element and its environment. A first feedback loop comprises (a) an input amplifier for amplifying a signal current from the MR element and (b) a source of bias current for biasing the MR element with a bias voltage. An input amplifier is concurrently biased by said current and amplifies a signal current from the MR element for producing a circuit output signal corresponding to dRh/RhRh and in which any differential direct current (dc) output offset error is minimized. (RhRh is the square of the time-averaged resistance of the MR element and dRh is the magnetic-signal-induced change in the resistance of the MR element.

Abstract: Apparatus and method for optimizing bus arbitration during direct memory access (DMA) data transfers across a nondedicated bus between a memory and/or a plurality of external devices each master having an arbitration priority. At least two nonoverlapping clocks are provided per transfer cycle and there is at least one transfer cycle per arbitration cycle. Arbitration priority requests are transmitted from each external device to an arbitration bus only at the rise of the first clock. At the end of the last clock, the priority code of the external device having the highest priority is determined to designate the external device which is to become bus master. Addresses and data are transferred between the designated bus master and the memory or another of the external devices via the nondedicated bus during the next cycle after a then active bus master relinquishes control. The priorities of the external devices can be changed dynamically.

Abstract: A rate 2/5 (2,18,2) code especially suitable for use with a resonant coil overwrite technique for magneto-optical recording. Serial binary input data is converted to serial binary code data that satisfies a (2,18,2) constraint and is reconverted to the serial binary input data. An encoder receives two sequential input bits and a five-bit state vector derived from an immediately preceding encoding operation, and generates a five-bit codeword and a new five-bit state vector based on the two input bits and five-bit state vector. A decoder converts the binary code data into five-bit codewords, converts each five-bit codeword sequentially into a reassigned three-bit codeword representation, then collects sets of four adjacent three-bit codeword representations. Each reassigned codeword representation is converted to a two-bit output corresponding to a then current set of said four three-bit codeword representations, and successive two-bit outputs are reconverted into the serial binary data.

Abstract: A time-dependent record depicting the motion of one or more selected atoms with a time resolution equal to or shorter than 10.sup.-12 second is generated by applying an electric field to a field emission tip. Electrons emitted from the selected atoms are focused into a beam which is swept over a spatially resolved electron detector for sensing the intensity of the beam as a function of time for creating the record. One- or two-dimensional records can be generated without signal averaging. The electrons can be directed onto a spot on a surface where dynamics are to be probed, and the electrons scattered or emitted from said surface are then focused into the electron beam. This method can also be used for transmitting information to a remote location at high frequency.

Abstract: A method and structure in which an adsorbate atom or molecule is repositioned on a substrate surface by moving the tip of an STM to a position adjacent to the atom to be moved and causing the atom to be attracted to the tip. While the atom remains bound to the surface (or, alternatively, is lifted), the tip is moved laterally to drag (or carry) the atom to a desired position at which it is bound to the surface.The atom may be repositioned in close proximity to an atom of the same or another type on the same or a different substrate to create a desired multi-atom structure or synthesize a molecule, or an atom may be removed to cleave a multi-atom structure, or a change in state of a multi-atom structure may be effected.

Abstract: A method and circuitry are described for sensing the clearance between a magnetic transducer and a moving magnetic recording medium in a magnetic disk or tape storage system or alternatively sensing the degree of magnetic instability of a magnetic transducer in such a system. Magnetic transitions prewritten on a preselected area of the medium are read to obtain a readback signal. The width of said signal is sensed at a predetermined amplitude level which is a preselected percentage of its base-to-peak amplitude to provide a voltage corresponding to the width of said signal at said level. The voltage is proportional to the width of the readback signal divided by the time period between successive transitions of identical polarity, so as to provide a measurement of clearance of degree of magnetic instability that is independent of the relative velocity between said transducer and medium.The voltage is digitized and compared to a prestored digital reference value.

Abstract: An actuator assembly for a magnetic recording disk file and method of fabricating same. A sleeve surrounds and is axially moveable relative to a stator to control the axial position of a head/arm assembly relative to a magnetic recording disk. The sleeve is separated from said stator by a gas-bearing film. Electronic circuit components are mounted on a canister that surrounds said sleeve and is substantially thermally isolated from said sleeve to dissipate heat generated by said components. The canister is in the form of a hollow rectangle which surrounds the rectangle sleeve with clearance and is secured to the sleeve at a minimum number of points to permit cooling air to flow through the clearance space with minimal obstruction. A flexible flat conductive input/output cable is secured to three sides of the canister, and a flexible flat conductive power cable is secured to the remaining side of the canister.

Abstract: A chemical filter assembly mounted in a breather opening in a housing for a magnetic storage device or other device to permit pressure equalization with the surrounding environment comprises at least one filter medium for removing particulate matter, and a unitary filter medium of a fabric of activated carbon fibers that is impregnated with a chemical that in combination with the carbon provides protection against both organic and inorganic gaseous or vapor pollutants, said fibers having a pore size small enough prevent significant penetration by aqueous solutions so that during impregnation the pores will not become clogged with the chemical.

Abstract: Direct overwriting of encoded data along a track in a magneto-optic recording medium is described. A laser beam, not modulated by data, is directed at the active side of the medium to locally heat the width of one track for conditioning it for direct overwriting. A magnetic head comprising an inductor and a capacitance in parallel with the inductor is movable in an appropriate manner to a selectable track. While the head is in alignment with the beam, current of a preselected polarity is supplied from a current source to the inductor. The current source is disconnected to reverse the field of the magnetic head by reciprocation of energy between the inductor and capacitance. Once the magnetic field is reversed, current is supplied to the inductor for maintaining the field until the next field reversal, the reversal times being determined by the data to be written.

Abstract: A rotary unit such as a disk file, retained in a dynamically balanced condition. In each end of the unit, there is an annular channel concentric with the rotational axis encircled by a flexible rim. A plurality of balls of substantially identical size and weight are inserted in an outer portion of each channel in which the balls are freely movable. While the unit is rotated at a speed above resonance, a balancing instrument is used to determine the mass magnitude and angle necessary to dynamically balance the unit. Then the balls are circumferentially relocated by vector balancing to provide mass at points equivalent to the determined mass and angle. The relocated balls are then forced axially past an interference ridge and into an inner portion of the respective channel in which the rim is flexed and the balls are held against movement.

Abstract: Storage capacity of a magnetic recording medium is increased by providing a nonconductive layer over a magnetic layer on which magnetic data is writable in a series of recording tracks, and applying a pattern of electrostatic charges to the nonconductive layer above at least one of the recording tracks to write track-position-denoting servo information in overlying relation to magnetic data. The pattern may be applied by electrostatic charges selectively of negative or positive polarity that are imprinted while the medium is in a mold or advanced over an electro-photographic charge transfer drum, for thereby preprinting the pattern as a step in fabrication of the medium.

Abstract: An amplifier circuit is disclosed for simultaneously producing electrical output signals whose magnitude is representative of signals produced by a magnetoresistive (MR) element and protecting said MR element from electrical short circuits between said element and its environment. A means including a first feedback loop biases the MR element with a bias current and amplifies a signal current for causing the MR element to produce a circuit output signal corresponding to dRh/Rh and in which any dc offset error is minimized. Rh is the resistance of the MR element and dRh is the magnetic-signal-induced change in the resistance of the MR element. A second feedback loop insures that the MR element is held at a preselected reference potential and concurrently insures that no current will flow sufficient to damage the element in event of a short circuit between the element and its environment.

Abstract: Airborne contaminants within a substantially sealed enclosure are detected and measured, in situ, without interrupting the operation of moving parts within the enclosure. At least one infrared (IR)-transparent attenuated total reflection (ATR) element, such as an optical fiber, optical fiber bundle, or ATR crystal, is disposed in the enclosure to collect or react with contaminants. An IR source is optically coupled to one part of the element, and an IR detector is optically coupled to another part of the element. The source and detector, in combination, respond to changes in intensity at the wavelengths of the IR radiation transmitted by the element to identify the contaminants and quantities thereof that settle on the element or compounds that have formed thereon. The source may be a continuous source (such as a black body) and the detector an IR spectrometer. Or, the source may be a diode laser and the detector an IR radiation detector.

Abstract: A method for coding a binary data string for a partial-response channel having a transfer function with a spectral null at zero frequency to provide a coding rate 8/10 and an output which is invariant to 180-degree phase shifts in the channel output signal. A finite-state machine is created having two pairs of states and a plurality of codewords each corresponding to a respective binary data byte. The binary data string is encoded by said machine into a string of binary codewords having a power spectrum value of zero for a frequency of zero. In response to each successive data byte in the binary data string, there is generated one of two complementary codewords from the one of that pair of the states designated by said machine as corresponding to the data byte for the then current state of the machine.

Abstract: A method and means is described for writing data on a recording medium, such as a disk or tape, containing servo samples in such manner that the number of servo samples is increased with a minimal increase in overhead (non-data) regions. The tracks on the medium are divided into a plurality of maxi sections, each of which contains all fields with servo and associated overhead information and also a data field. At least one micro servo section containing only a portion of said information is located within each data field.As each micro servo section passes by an associated recording head, writing and reading of data is temporarily interrupted, but resumed when the micro servo section moves beyond the head, in such manner as to require minimal resynchronization of said data during reading.Using a phase continuous clock, data is written in both portions of a data field to either side of each micro servo section in one pass of the disk or tape relative to the head.

Abstract: A method and servo system is provided to compensate for misalignment of separate read and write heads when reading and writing data on a magnetic disk.Two sets of servo information are generated for each data track on the disk. These sets are radially displaced with respect to each other by a distance equal to the respective misalignments between the read and write heads at each respective data track. One set is generated by the write head. The other set is generated by the write head while the read head is positioned using said one set as a position reference. Thereafter, to write data on a selected track, the read head is first aligned with said one set of servo information and then data is written on said track with the write head. To read data on a selected track, the read head is aligned to said other set of servo information and then the data is read by said read head.

Abstract: A method for implementing error-correcting codes for disks, wherein the statistics of error vary according to the radius of the location being accessed.A Reed-Solomon code is selected having data bytes and redundant bytes and an error-correcting capability sufficient to protect against an anticipated worst case or errors.The number of redundant bytes in that code, and thereby the number of correctable errors, is progressively reduced in respective concentric areas of the disk according to the statistics of error for such areas, for thereby progressively reducing the number of correctable errors as the need for error correction capability decreases.For multiband recording, the areas are concentric bands in each of which data is recorded at a clock frequency substantially proportional to its inner diameter; and in such case, the number of redundant bytes is reduced progressively in each successive band toward the innermost band.

Abstract: The channel characteristics of magnetic-disk storage devices vary with track radius. An adaptive three-tap transversal equalizer that compensates these variations for systems using partial-response signaling is presented. The equalizer coefficients are updated by applying a procedure that is related to the recursive least-squares algorithm. This new updating procedure does not require multiplications and is well suited for high-speed implementation. Results obtained by computer simulations and measurements with a prototype have shown that the proposed adaptive equalizer can effectively compensate variations in magnetic-disk channel characteristics with track radius.

Abstract: A magnetoresistive (MR) read head in which an insulator layer defines the effective track width over which the read head is sensitive. The insulator layer is deposited or patterned to extend a predetermined distance over the MR element, and the predetermined distance is chosen equal to the desired track width. Conductor leads are deposited in contact with the regions of the MR element not covered by the insulator layer with the conductor leads extending up to, and possibly overlapping, the edges of the insulator layer so that the read signal is sensed over the length of the MR element covered by the insulator layer.