Abstract: The invention provides illumination and may provide magnified viewing of an object using a means which may be located directly in front of a seated or reclining individual, while providing for the means to pivot out of the way for easy egress from the sitting or reclining position. The invention provides a counter weight at a fixed radius for stability, and to facilitate the user's easy assessment of whether the counterweight will contact or interfere with nearby objects. The use of the fixed radius counterweight provides utilities that are not achieved when using a variable radius counterweight, or a weighted base configuration.

Abstract: A data processing system and housing are disclosed having reduced electromagnetic energy emissions. A central processor is mounted within a generally rectangular conductive outer case which includes one or more apertures for receiving and mounting electronic subassemblies such as: diskette drives; fixed disk drives; tape drives; and, optical disk readers. A conductive waveguide assembly having at least one waveguide is then mounted within the conductive outer case with one end of the waveguide mated conductively to the aperture within the conductive outer case. Electromagnetic energy from the electronic subassembly or from within the conductive outer case must then traverse the conductive waveguide prior to emission from the data processing system housing through the aperture therein. The shielding effect of requiring electromagnetic emissions to traverse an internal waveguide will provide substantial attenuation of electromagnetic interference.

Abstract: An optical tool is disclosed which permits a sequence of aligned transducer gaps to be positioned parallel to the axis of a disk file. The tool is surfaced with transparent material, has a thickness the same as the disk or disks of a disk stack being simulated and presents an etched alignment grid at the interface surface between transducer and tool. The virtually common plane of the transducer gap and etched grid substantially eliminates parallax and the unfilled etched grid permits the gap to be seen, whether aligned with the transparent unetched surface or the translucent etched surface portion. The use of inclined mirrored surfaces underlying the grid permits alignment to be effected using a bright field microscope and observing from a direction rotated 90 degrees from a line perpendicular to the grid to enable alignment of transducer gaps confronting one another at opposite sides of the disk.

Abstract: A sector servo seek control samples each sector to obtain sector time, the track identification within a sequence of track types and a position error signal for a track location to track location seek. The device during each sector determines the actual transducer track location and the next sector projected track location with respect to the sequence of track types. The projected track location is corrected using the error signal to find the actual location, but if a sector signal is missing or erroneous, the projected location is used as the actual location, permitting a composite correction to be made when a correct sector signal is obtained. The seek time is minimized by using maximum acceleration followed by maximum deceleration while not exceeding a velocity value that would cause the device to overshoot the target track using full deceleration.

Abstract: The servo system includes the use of servo signals of four types such that each group of four adjoining servo tracks identifies the center line of a data track of interest and presents unique signals from the respective four servo tracks. The analog value of the signals are stored and sensed to provide a substantially linear position error signal over a three-track wide region. By using variable gain with respect to the analog signals, compensation for the variance between data head width and track pitch, and a quadrature servo portion, linearity can be achieved. In addition, since the substantially linear region is three tracks wide and the position error signal does not become ambiguous over a width of four tracks, a one-track seek can be accomplished using an error signal rather than a seek.

Abstract: A disk file is equipped with a recirculating filter duct utilizing the pressure differentials within an enclosure imparted by the rotating disk to induce an air flow in the duct having an inlet near the disk periphery and an outlet effectively radially inward thereof. The flow of air through this duct is enhanced by a deflector adjacent the duct outlet at the side thereof initially approached by a given point on the rotating disk and a projection approaching the opposite surface of the disk or disk pack and generally axially aligned with the deflector to equalize the forces exerted and avoid instability of disk operation. The duct is configured to eliminate eddy currents and the air volume within the enclosure is limited to increase the rate at which air changes occur.

Abstract: Analog voltage levels derived from optically scanning a document or from magnetically scanning a magnetic record, depend upon the variable amplitude of a background signal. The analog voltage levels are processed by a bucket brigade circuit to set a threshold from which a binary decision may be made as to the presence of a black or white indicium in optical recognition or a one (1) or zero (0) bit in magnetic reading.

Abstract: Circuitry for providing a high speed access by a swingable arm and a transducer carried thereby across a plurality of tracks on a rotatable data storage device to a target track on the rotatable device including a speed indicating circuit connected with the transducer for indicating the speed of the transducer in crossing tracks on the rotatable device and a switchable filter effectively between the transducer and said speed indicating circuit which has a high roll off as the transducer crosses the tracks at a high speed and has a low roll off as the transducer approaches the target track at a relatively low speed so as to thereby cause the speed indicating circuit to accurately indicate the speed of the transducer in moving across the tracks of the rotatable device.