Abstract: A method and circuitry are disclosed for suppressing additive transient disturbances in a data channel; e.g., due to thermal transients caused by an MR transducer contacting moving a storage surface. Positive and negative envelope detectors each have their inputs connected to the channel, and provide respective outputs which are summed and contain an envelope component and a residue component. A buffer interconnects the detectors to allow both detectors to follow rapid positive excursions of the data channel signal. A nonlinear signal-adaptive filter is connected to the summed output to further reduce the residue component. The data channel signal (or preferably the output from a delay means connected to the channel) is summed with the output from the filter. The relative amplitudes of these two outputs is set such that the resulting summed output signal is free of additive disturbances.

Abstract: An apparatus and a method for fast acquisition of the sample-timing phase in systems using partial-response signalling are disclosed. For fast initial adjustment of the timing phase, a known preamble is transmitted. During that phase, previous schemes could occasionally hang up for an extended period of time at the unstable equilibrium point halfway between the desired sampling times. The new procedure eliminates the hangup problem by introducing a hysteresis effect which greatly diminishes the probability of reversals in the once chosen direction of timing-phase adjustment. Thus, reliable adjustment of the timing phase with a much shorter preamble is achieved. The apparatus for furnishing a timing correction signal .DELTA..tau..sub.n includes a timing gradient generator portion (41) and a data sample reconstruction portion (43). The data sample reconstruction portion (43) develops a present reconstructed data sample x.sub.n from the present received signal sample y.sub.

Abstract: An improved method is described for coding input strings to improve reliability of partial response channels. This method comprises encoding an input string into an intermediate string using a binary convolutional code, and encoding the intermediate string using a nonlinear inner code that repeats and inverts selected bits of the intermediate string. The inner code has a coding rate of less than one. As specifically illustrated, this method provides coding gains for partial response channels of at least 4.8 dB.

Abstract: A method is disclosed for coding input strings for a partial response channel to provide an output having a reliability determined by a preselectable coding gain. This method involves determining each frequency at which there is a zero in the transfer function of the partial response channel, and then encoding an input string into a binary code string having a power spectrum value of zero for each such frequency. A channel output sequence is generated responsively to transmission of the code string through the channel. The most probable sequence among those having a power spectrum value of zero is then calculated from the channel output sequence and decoded to provide the output.

Abstract: A pulse signal conditioner filters and equalizes signal pulses representing digital data whether or not obtained from a magnetic recording device. Modified low pass filters filter the pulse signals and also derive and feed forward the second time derivative of the filtered pulse signals. The filtered pulse and the second time derivative thereof are combined to slim the pulse. Further slimming is provided by delay line equalizers having three paths. A first path for attenuating the pulse signals, a second path for delaying the pulse signals for a first delay, and a third path for delaying the pulse signals for a second delay and attenuation. Pulse signals from the three paths are combined to further slim the pulse.

Abstract: A method for optically measuring at least one characteristic of a thin film on a reflecting substrate. A p-polarized beam of collimated light of known intensity is directed through an integrating sphere onto the film at substantially the Brewster's angle of the film. All the light is reflected into the sphere, including all diffusely reflected light as well as the light specularly reflected at a region inside the sphere where the specularly reflected light is incident. A reflective surface is provided for determining the thickness of the film as a function of the total intensity of light sensed within the sphere. An absorptive surface is provided at said region for absorbing the specularly reflected light for determining the porosity or surface roughness of the film based on the intensity of the diffused light sensed within the sphere not reflected from the substrate.

Abstract: Direct overwrite of data on magneto-optic medium is described. Old data is erased and new data is written during a single rotation of the media in a data storage system which includes a resonant coil for producing a high frequency alternating magnetic field interacting with laser pulses having a duration equal to a small fraction of the period of the magnetic field. Variable-length magnetic domains are formed by overlapping circular magnetic domains to provide pulse width modulation (PWM) encoding of data.

Abstract: A method termed Even Mark Modulation (EMM) is disclosed for coding input strings for input-restricted (1+D) or (1+D).sup.2 partial response channels that require at least one pair of consecutive signals of one state in order to record or transmit data to a receiving device. EMM provides improved coding gains and is especially suitable for optical recording.An input string is encoded into a binary code string in which all one-state signals (e.g., "1's") are in the form of runs of at least one contiguous pair; however, signals of an opposite state (e.g., "0's") may be of any length or duration. The EMM signals are detected with a maximum likelihood detector using an algorithm based on a three-state trellis structure for (1+D) channels and a five-state trellis structure for (1+D).sup.2 channels adapted to the particular partial response channel. In a preferred embodiment, the coding rate is 2/3 and the coding gain is at least 3 dB unnormalized and at least 2.2 dB when normalized.

Abstract: A method and apparatus is disclosed for correcting up to two byte errors in encoded uncorrected data in records of a predetermined length. As illustrated, the records are subblocks of a block in a multi-level error correction code format. The data is read from a storage device and corrected by decoding and processing four syndromes of error (S.sub.1, S.sub.2, S.sub.3, S.sub.0) that are generated by means disclosed in the prior art. These syndromes are decoded in response to uncorrected errors in any one record by computing vectors (P, Q, and R), which are functions of the four syndromes. Binary numbers (u and v) are then determined from these vectors by table look-up to enable calculation of one value (d) from the sum of said binary numbers for determining error locations. Another value (t), mathematically related to said one value, is then determined by table look-up and the error location values (y and z) are determined by calculating the offset of binary numbers (u,v) from the other value (t).

Abstract: A self-diagnostic method and apparatus is described for indicating the likelihood of an impending crash of a magnetic transducer or head with a rotating magnetic medium by dynamically and periodically calculating overwrite efficiency for performing a desired control operation when it exceeds a preselected value denoting dangerous proximity of the transducer to the surface of the medium.

Abstract: A two-pass method for relocating a set of linked control blocks stored away on a persistent medium after a first pass and then rewritten into internal memory of a computing facility during second and subsequent passes each time an application to which the control blocks are bound is executed. The first pass involves path following and coloring pointers affected by the relocation, mapping discontiguously located blocks into a linear address space, changing affected control blocks to location offsets, and writing out the linked control blocks to DASD store. Upon the second pass, virtual addresses are substituted for the offsets upon rewriting of the control blocks to internal memory.

Abstract: A method and apparatus is disclosed that is selectively conditionable, during read processing, to operate in normal or diagnostic on-the-fly mode or in normal or diagnostic deferred mode to correct errors in encoded uncorrected data in a disk storage device. During deferred mode operation, hardware in the disk storage device receives uncorrected data in real time and generates syndrome bytes which are decoded at the device into error pattern and error location information that is transmitted to a storage director. Circuitry is provided for retaining, if desired, error pattern and location information to facilitate identification of surface defects in the storage disk whether read processing was done on-the-fly or in deferred mode.

Abstract: The storage unit comprises an array of tunnel tips (13) arranged at tunneling distance from a recording surface (2a) of a storage medium (2) which is capable of permitting digital information to be written or read through variations of the tunneling current. The storage medium (2) is attached to the free end of a piezoceramic bendable tube (3). In operation, the free end of the tube (3) is moved in a circular orbit by repetitive sequential energization of oppositely arranged pairs of 90.degree. phase shifted electrodes (4,6 and 5,7). This tube movement causes each tunnel tip (13) to scan a respective unique associated annular area of the storage medium (2). To address a particular concentric track in a particular annular area, tunneling current is applied to the associated tip (13) via respective electrodes (16,18) while, concurrently, a potential is applied via electrodes (4,6 and 5,7) to tube (3) of a magnitude corresponding to the desired orbital diameter for the tube.

Abstract: A voltage controlled oscillator (VCO) having high temperature stability and wide voltage/frequency linearity is provided. The VCO comprises a multivibrator being switched by a bipolar type device, and temperature fluctuations of the bipolar type means are compensated by a FET current source coupled thereto. To provide a linear relationship of frequency vs. voltage over wide voltage range, the bipolar device is further regulated by a plurality of resistor and diode networks.

Abstract: An edge-triggered latch is disclosed which has a low setup time and almost no metastability problem. It comprises a dynamic sensing means for detecting the voltage level of the data signal and at least one dynamic buffer for amplifying said detected voltage level into one of two logic levels recognizable by a static latch wherein the sampled result is stored.

Abstract: To increase storage capacity of a disk storage device, the recording surface of the device is partitioned into a plurality of concentric recording bands, data to be recorded on respective bands are encoded using different run-length-limited codes with the code rate of each band being higher than the adjacent inner band.

Abstract: A process and apparatus are disclosed for producing a beam of coherent radiation at essentially 459 nm by mixing, in a nonlinear crystal consisting essentially of KTP, two laser beams, one at essentially 1064 nm and the other at essentially 808 nm. The 1064 nm radiation is derived from a Nd:YAG laser that consists of an input mirror, an output mirror and a Nd:YAG crystal, and contains also the KTP crystal. The Nd:YAG laser is pumped by an essentially 808 nm semiconductor diode laser beam, which passes through the input mirror and through the KTP crystal into the Nd:YAG laser crystal where it is absorbed. The 1064 nm radiation oscillating inside the Nd:YAG laser resonator is mixed either with the said 808 nm pump beam or with 808 nm radiation provided by a second semiconductor diode laser whose light is coupled with the 1064 nm beam using a beamsplitter. The essentially 459 nm beam passes through the output mirror to a utilization device.

Abstract: A low flow rate-low pressure atomizer device is disclosed which is so dimensioned and operated as to accelerate a gas to substantially sonic velocity and cause it to break up a cleaning liquid into small droplets and accelerate these droplets to at least half the velocity of said gas to create shear stress at a surface closely adjacent the exit end of said device, thereby to remove contaminants or the like from said surface.

Abstract: An amplifier for voltage biasing and amplifying the signals produced by a magnetic sensor is provided. Electrically, the resistance of the sensor is disposed between the bases of a differential pair comprising the input stage of the amplifier. Constant bias voltage for the sensor is provided independently of sensor resistance. DC feedback to the input stage balances current flow in both paths of the differential input stage to correct for DC offset arising in the output from input stage emitter resistor. The amplified signal, representing .DELTA.R.sub.h /R.sub.h, is sensed as a voltage across the magnetoresistive sensor, where .DELTA.R.sub.h is the change in steady-state resistance, R.sub.h, of the sensor.

Abstract: An improved method is described for transmitting facsimiles of scanned symbols. Prototype facsimiles of each symbol in a library are enhanced by averaging the representations of each scanned symbol with a respective previously created prototype facsimile for that symbol. The amount of white space at opposite sides of each symbol prototype is determined. The enhanced prototype facsimile for each scanned symbol is associated with positional parameters denoting the average white space at said opposite sides of each symbol.