Abstract: A timing circuit for a track following servo system wherein an odd servo track having a series of prerecorded odd dibits thereon and an adjacent even servo track having a series of even dibits prerecorded thereon are moved with respect to a servo head to induce in the servo head signals that vary with the occurrence of the dibits and have an amplitude representative of the lateral position of the servo head with respect to the servo tracks. The servo head and its associated preamplifier produce a first signal having portions from both odd and even servo tracks and a second signal that is the inverse of the first signal. The first and second signals are processed by parallel identical circuit paths to generate a clocking signal that times the remainder of the data storage system in synchronism with the spacing of dibits on the servo tracks.

Abstract: A method and apparatus for accessing data blocks in a computer system having multiple-disk drive rotational position sensing which is not centrally synchronized and where data read and write requests are normally weighted by the order of availability of requested data blocks. The weighting of the priority, or queue position, of selected data blocks is modified by advancing the apparent initial location of data blocks designated for preferental access and maintaining an availability signal, or peripheral interrupt, for an extended period. A special pre-data-transfer instruction indicates the duration of the peripheral interrupt. A circuit for implementing the invention has a storage register for receiving the special instruction, a down counter for decrementing for the duration of the designated pre-data-interrupt and an interrupt duration control latch for issuing and extinguishing the interrupt.

Abstract: A phase comparator for a digital phase locked loop which provides first and second order error signals for phase and frequency correction of a voltage controlled oscillator in the loop with respect to data being read for self synchronization of the data. A first order error signal is generated in a first phase detector which operates only during a VCO "unsafe" condition, i.e., when a data pulse is beyond a present limit. A finer, second order error signal is generated in a second phase detector which operates only during a VCO "safe" condition, i.e., when a data pulse is within a preset limit.

Abstract: A phase lock system for locking the output pulses of a motor driven tachometer in phase with reference pulses that recur at a prescribed reference frequency. A phase/frequency detector operates in a frequency mode when there is a frequency difference between the output pulses and the reference pulses so as to generate an error signal indicative of the frequency difference and a saturating amplifier coupled between the phase/frequency detector and the tachometer motor responds to the error signal to provide maximum drive power to the motor so as to vary the tachometer and drive the output pulse frequency toward the reference pulse frequency at a maximum rate. When frequency equality is achieved, the phase/frequency detector operates in a phase mode in which the phase error between the output pulses and the reference pulses is measured at a time when the system is still in saturation because of its high gain.

Abstract: A circuit for discriminating among pulses in a series of recurring pulses based on the interval between adjacent pulses which circuit is particularly useful in extracting timing information from a series of pulses such as are induced in a servo head by movement relative thereto of a prerecorded servo track in a disc pack data storage system. The circuit includes a monostable multivibrator for producing a timing signal having a duration corresponding to the time interval between two successive pulses. The monostable multivibrator output is stored, for example in a data flip flop, so as to produce an output pulse from the flip flop if a succeeding pulse in the series occurs while the monostable multivibrator output is high.

Abstract: A servo system for accurately positioning a transducer relative to data paths on a recording medium by detecting sync and servo signals from two parallel abutting servo tracks sharing a common longitudinal boundary within circumferentially spaced sectors of the medium. Within each sector of the recording medium, two servo waveforms of different frequencies in two abutting servo tracks are preceded by a sync reference waveform of the same frequency in both servo tracks which is used as a reference for a phase locked oscillator, connected to the transducer, generating a pair of modulation signals that are to be mixed with transducer signals from both servo waveforms. A pair of servo channels are provided for receiving the pair of modulation signals and the servo signals for deriving an imbalance error signal representing deviation of the transducer from the center line of a data path, which is the projection from the sectors of the common longitudinal boundary between servo tracks.

Abstract: An electronic tachometer comprising an integrator having its output coupled to a variable gain amplifier and responsive to an input signal representative of the acceleration of a moveable load, such as a head assembly of a disk drive, for producing a coarse velocity signal at the output of the variable gain amplifier indicative of the load velocity, a tachometer gain correction circuit including another integrator coupled to receive the coarse velocity signal to produce a coarse distance signal indicative of distance traveled by the load and means for combining the coarse distance signal with a reference distance signal to produce a distance error signal which functions to adjust the gain of the variable gain amplifier so as to vary the coarse velocity signal to make the coarse distance signal equal to the reference distance signal, and accumulative error compensation means coupled to receive a gain indicative signal derived from the distance error signal to produce a signal input to the tachometer integrator

Abstract: Apparatus for controlling the velocity of a moveable load, such as the magnetic head assembly of a disk drive, comprising means for providing velocity command and velocity feedback signals which are combined to produce a velocity control signal for moving the load at desired velocity and additional means including an integrator and sample and hold circuit for detecting error in the feedback signal and varying the command signal to compensate for such error so that the load is controlled to move at the desired velocity.

Abstract: A word processor system comprising a typewriter, a data storage unit, a tab stop register for storing signals representative of tab stops set on the typewriter and means for controlling the tab stop register to keep it aligned with the typewriter carrier during the course of typing including backspacing, carrier return and tabbing actions. Additional means responsive to tab command and tab stop signals is provided for recording a tab action in the data storage unit as a succession of encoded space signals equal to the number of typing positions to the next tab stop from the carrier position at the instant of the tab command.

Abstract: A magnetic read/record head having a layer of uniaxially anisotropic magnetic material as the pole faces, which increases the ratio of magnetic reluctance between the pole faces to the magnetic reluctance along the fringing flux path through the recording medium. Two embodiments of the invention are disclosed, one embodiment providing a layer of anisotropic magnetic material in a continuous layer around a complete loop from one pole face to the other pole face, and the other embodiment providing a layer of anisotropic magnetic material confined to each of the pole regions.

Abstract: A dual channel signal detector circuit comprising an equalizer for responding to a variable peak amplitude input signal, in which the peaks are representative of data, so as to provide a substantially constant peak amplitude output signal having discrete data representative pulses spaced along a base line, which is substantially flat at the zero level in regions intermediate the pulses, for application to separate peak detection and amplitude detection channels. The peak detection channel produces data pulses each indicative of the relative time occurrence of the peak of a respective data representative pulse while the amplitude detection channel is triggered by signal levels of the data representative pulses exceeding a predetermined threshold to produce gating pulses for gating the data pulses to the circuit output substantially exclusive of any noise that may be present at the input of the circuit.

Abstract: A phase detector for use in data systems which recovers data from a recorded media, which phase detector operates in a nonharmonic mode during the period of synchronization of the clock frequency and phase with that of preamble data, and operates in a harmonic mode during actual data recovery.

Abstract: An electromagnetic actuator is disclosed having a magnetic circuit which provides a plurality of annular, concentrically located air gaps and a plurality of annular actuator forms which are positioned in the air gaps. A winding is mounted on each of the forms and each winding is adapted when electrically energized to establish a field which reacts with a field of the magnetic circuit and causes rectilinear motion of the form in an axial direction. A single magnetic circuit is thereby provided for a plurality of actuating forms and advantageously reduces the iron requirements of the actuator.

Abstract: A multi-jet ink printer comprises a drum having rows of pointed jet formers, or prongs, mounted about its outside surface. The drum is successively rotated such that the tips of the prongs are dipped into a reservoir of ink and thereafter pointed toward a recording carrier, such as paper. When the prongs are directed toward the carrier, an electrostatic field is established between the drum and electrodes located on the opposite side of the carrier. The ink is thereby caused to leave the sharp points and form ink jets composed of very small droplets of ink. The ink is thereby deposited on the carrier. There is an electrode located opposite each prong which is selectively energized to produce dots on the carrier when the prong is in selected positions relative to the carrier. In this respect, the drum is moved axially (horizontally) to scan rows on the carrier, and the carrier is moved longitudinally (vertically) to scan vertically on the carrier.

Abstract: To develop a latent image, which exists in the form of different potential values on different areas of a substrate, an auxiliary substrate is coated with toner by charging the toner triboelectrically and applying a potential to propel the charged toner onto the auxiliary substrate. This toner-coated substrate is brought into close proximity with the image forming substrate, while being maintained at a potential which lies between the different potential values of the latent image.

Abstract: An improved method and apparatus for the storage of binary data on a magnetic surface is described. The binary data to be stored is provided in the form of electrical pulses occurring sequentially at intervals of time T. The method and apparatus provide for exciting a recording head and causing a flux transition at a first predetermined time T.sub.1 during the data pulse interval in order to store a first binary character or, alternatively, for exciting the head at a second predetermined time T.sub.2 for storing a second binary character. A minimum transition separation time T.sub.min equal to the interval period T is established by inhibiting excitation of the head at those times which are separated from another transition by a period of time less than T. A limited maximum transition separation time T.sub.max is provided by shifting the excitation of the head in an interval immediately adjacent an interval during which excitation of the head was inhibited.

Abstract: A mechanized file comprising a plurality of article storage carriers pivotally suspended from and controllably transported by a closed loop conveyor mechanism for selectively positioning the carriers at an operator work station. A first pair of diagonally disposed rollers is provided on one side of each carrier and a second pair of diagonally disposed rollers, oriented transverse to the first pair, is provided on the other side of each carrier. Tracks are arranged on each side of the file for engagement with the rollers to limit tilt of the carriers while being transported by the conveyor mechanism.

Abstract: A phase detector comprising three bistable flops and a NAND gate interconnected to respond to a data input pulse stream and a controlled square wave clock pulse stream to provide, in response to each data pulse, a reference pulse having a width equal to one-half the clock pulse period and a variable pulse having a nominal width equal to that of the reference pulse and a proportionately greater or lesser width according to the direction and amount of displacement of the data pulse from the center of the clock period in which it occurs.