Abstract: In a tracking system using an error signal derived from recorded dipulses of opposing polarity on each side of the center of a data track recorded on a magnetic medium, the need for highly accurate signal integration is avoided by partially integrating the dipulse signal, and then integrating the partially integrated signal above a predetermined threshold. The resulting double-integrated signal provides an error signal substantially unaffected by DC and noise offsets. A double-ended average pulse detector with feedback using a double-ended "current mirror" to carry out the described method is disclosed.

Abstract: Apparatus adapted for use in printers for indicating when the paper upon which information is to be printed has been depleted. A pivotable sensing member is slightly biased towards a fixed guide member, the two members being adjacent to one another. The sensing member has a horizontal row of protrusions on its inner wall which entend towards the opposing wall of the fixed member. The opposing wall of the fixed member similarly has a horizontal row of protrusions extending towards the sensing member but being aligned between the protrusions on the sensing member. In the situation wherein no paper is introduced between said members, a switch associated with the sensing member provides an indication to control circuiting that no paper is present for printing.

Abstract: A phase-sensitive transducer apparatus comprises first and second relatively movable members, the first relatively movable member having a plurality of windings and the second relatively movable member having a winding. Means are included for applying a first input signal to one of the windings of the first relatively movable member and a second input signal to another of the windings of the first relatively movable member. An output signal is developed on the winding of the second relatively movable member. The first and second input signals are sinusoidal in nature of substantially identical frequency and peak amplitude and are phase-displaced by a predetermined amount, and the output signal is substantially constant in peak amplitude and variable in phase during relative movement of the first and second relatively movable members.

Abstract: A serial printer comprises a carriage, a print member rotatably mounted to the carriage and including a plurality of character elements, a first drive coupled to the print member for rotating the print member to a desired rotational position in order to place a selected character element at a printing position adjacent a record medium to be printed upon, a second drive coupled to the carriage for moving the carriage along a predetermined path whereby the print member is caused to move to a desired printing position along the path, a first servo control coupled to the first drive and responsive to a first set of input data and instructions for controlling the direction and speed of rotation of the print member, a second servo control system coupled to the second drive and responsive to a second set of input data and instructions for controlling the direction and speed of movement of the carriage, and a programmed data processor coupled to the first and second servo control system for supplying at least some of

Abstract: An exerciser is provided for use with a disk drive of the type having a microprocessor, a first memory for storing microcoded control programs for the drive, a second memory for storing instructions for the head carriage servo control apparatus, an address bus for supplying address signals from the microprocessor to the first and second memories, and a data bus for supplying program instructions from the first memory to the microprocessor, and for supplying instructions from the second memory to the servo control apparatus. The exerciser developes track address signals that are supplied onto the data bus for application to the microprocessor. A third memory is included in the exerciser for storing diagnostic programs. A decoder is also included for decoding an address signal on the address bus in order to generate a new address signal for the third memory. Program instructions accessed from the third memory are supplied onto the data bus for application to the microprocessor.

Abstract: A data processing apparatus for processing digital data in accordance with a plurality of predetermined tasks of preassigned priority values and identified by a respective plurality of devices connected to the data processing apparatus. Each device is capable of generating the respective task request signal when requiring service by the data processing apparatus.

Abstract: A disk drive includes a first memory for storing microcoded program routines and sub-routines for the drive. One of the routines is a main program routine that is comprised of a plurality of service routines executable in sequence during a respective plurality of time-slots of the main program routine processing cycle. One of the service routines includes a plurality of service sub-routines executable in sequence with only one being executed during each processing cycle. The drive also includes a second memory having a register therein respectively associated with said one service routine. The register is capable of storing the addresses of locations in the first memory at which program instructions for said one service routine are stored.

Abstract: A data processing display system comprises a display device capable of displaying a desired image and including a plurality of points each capable of being selectively illuminated. A main memory storage device is also included in the system and comprises a plurality of addressable storage locations, each location capable of storing a multi-bit display word therein. At least some of the addressable storage locations include in the aggregate a number of bits at least equal to the plurality of points of the display device. A display bit map of the desired image is thus capable of being stored and defined in the at least some addressable storage locations.

Abstract: A data recording and reproducing system in which a disk having a plurality of data tracks has a track following code stored thereon, enabling a recording head moved by a servo system to be centered in relation to a desired track. The code includes, on one side of the track centerline, first regions of magnetic flux in which there is a first area of magnetic flux reversal, and, on the other side of the track centerline, second regions of magnetic flux in which there is a second area of opposite flux reversal adjacent the first area. The lines of flux in each area are equal. A recording head, when centered on the track centerline, detects no difference in the number lines of flux between the first and second areas due to its self-nulling properties, though the output signal of the head, which represents the rate of change of detected flux as the head traverses the two areas, may show differences at different points in time of detection.

Abstract: A repeater is provided for use in a communications network which includes a plurality of transceivers, the repeater being bidirectional and allowing the interconnection of two segments of the network and also allowing longer communications networks to be used by matching or amplifying the signal level of an incoming information packet on one segment and coupling the matched or amplified signal to a succeeding segment. The repeater has two ports that preferably utilize two semiconductor chips, each port having a carrier one-shot which detects the presence of an information packet arriving at that port. If an incoming port's one-shot is triggered by an incoming packet of information, the carrier one-shot for the repeating port and the incoming port transmitter are disabled.

Abstract: In connection with a head positioning device for magnetic disc drives in which a low cost implementation for seeks of varying lengths is important and optimum seek time is secondary, a system is disclosed in which head velocity, at least during the final portion of the deceleration phase, is a linear function of the distance remaining to target. In addition, the system lends itself to the approximation of optimum seek time on long seeks by commanding a velocity curve whose slope exceeds the maximum deceleration of the torquer for all but the final portion of the seek distance so as to provide a maximum acceleration-deceleration profile until just prior to the target, and a final deceleration at a decreasing rate as the head approaches the target.

Abstract: A velocity control apparatus for a disk drive of the type comprising a recording disk rotatable about its axis, an electromagnetic read/write head for reading data from and writing data onto tracks on a surface of the disk, and means coupled to the head and responsive to velocity command signals for controlling the direction and speed of movement of the head. The velocity control apparatus includes a memory divided into a plurality of sections respectively associated with different ranges of desired distances to be traveled by the head, each section containing a predetermined number of addressable storage locations together defining an approximation of a desired velocity trajectory curve for a desired distance to be traveled included within the range associated with said section.

Abstract: An inductive transducer includes first and second relatively movable members, the first relatively movable member having a plurality of windings and the second relatively movable member having a winding. The windings of the first relatively movable member each have a pair of terminals and are each arranged in a pattern comprised of a first section coupled to one of the terminals and a second section coupled to the other terminal and to the first section. Each section includes a plurality of conductors oriented substantially parallel to one another wherein immediately adjacent conductors of such section are capable of conducting current in opposite directions and are coupled to one another by an end-segment arranged substantially perpendicular to the conductors.

Abstract: A serial printer comprises a carriage, a print member rotatably mounted to the carriage and including a plurality of character elements, a first drive coupled to the print member for rotating the print member to a desired rotational position in order to place a selected character element at a printing position adjacent a record medium to be printed upon, a second drive coupled to the carriage for moving the carriage along a predetermined path whereby the print member is caused to move to a desired printing position along the path, a first servo control coupled to the first drive means and responsive to a first set of input data and instructions for controlling the direction and speed of rotation of the print member, second servo control means coupled to the second drive and responsive to a second set of input data and instructions for controlling the direction and speed of movement of the carriage, and a programmed data processor coupled to the first and second servo control system for supplying at least some

Abstract: A printing apparatus includes a supply of printing material, a drive assembly coupled to the printing material and capable when enabled of advancing the material along a predetermined path past a printing station, and a detection device for detecting when the printing material fails to be advanced by at least a first predetermined amount when the drive assembly has been enabled to advance the material by at least a second predetermined amount.

Abstract: A disk drive comprises a housing having a door through which a cartridge including a recording disk therein may be inserted. A spindle drive assembly is mounted in the housing and is responsive to a first set of instructions for rotating the recording disk of a disk cartridge loaded into the housing through the door and onto the spindle drive assembly. An actuator is also mounted in the housing and is capable of controlled reciprocal movements relative to the axis of rotation of the spindle drive assembly. A head carriage assembly is mounted in the housing to the actuator and includes at least one electromagnetic read/write head thereon for reading data from the writing data onto tracks of the recording disk of a cartridge loaded onto the spindle drive assembly. Servo control apparatus is mounted in the housing and is responsive to a second set of instructions for controlling the speed and direction of the reciprocal movements of the actuator.

Abstract: A method and apparatus for restoring the electromagnetic read/write head of a disk drive from a position between a data-field track located closest to the axis of rotation of a disk loaded in the drive and a data-field track located furthest to such axis of rotation, to a position over the latter data-field track. A first predetermined code is prerecorded on each data-field track and a second predetermined code is prerecorded on each of a plurality of guard-band tracks. The head is first moved in a direction away from the axis of rotation of the disk at a predetermined velocity. The code stored on each track is read and detected as the head is moved thereover. The head is stopped over a track when the code read and detected therefrom is the second predetermined code. Then, the head is moved in a direction toward the axis of rotation of the disk and stopped over the data-field track located furthest from the axis of rotation of the disk.

Abstract: A dot matrix printer including a single printhead having two columns of print wires, the wires in one column being used to print only odd numbered dot columns on a record member and the wires in the other column being used to print only even numbered dot columns on the record member. In one embodiment the wire columns are spaced apart a distance equal to an even number multiple of the space between two adjacent dot columns and the wires in each column are then energized alterntely as the printhead traverses the dot column positions. In another embodiment the wire columns are spaced apart an odd number multiple of the space between two adjacent dot columns and the wires in each column are then energized simultaneously as the printhead traverses the record member.

Abstract: Decoding apparatus for separating clock and data pulses from a double-frequency pulse train, including a retriggerable window one-shot, a bit shift compensation circuit, clock rate tracking means, data bit and clock bit gates, means for keeping track of whether a specific pulse is a data pulse or a clock pulse, and means for actuating the data bit and clock bit gates, based on the status of the system and the state of the window one-shot. The apparatus also provides means for detecting when a clock pulse is missing, including circuitry which simulates the detection of a clock pulse to the rest of the device to keep the system status and timing properly synchronized to the pulse train data.

Abstract: A ribbon cartridge comprising a housing, a supply reel containing a supply of ribbon wound thereon, a take-up reel, means for rotatably mounting the supply reel at a first location in the housing, means for rotatably mounting the take-up reel at a second location in the housing, the second location being spaced both vertically and horizontally from the first location, and means for transferring ribbon along a predetermined path from the supply reel onto the take-up reel.