Abstract: A metastable prevent circuit comprises a plurality of parallel channels, each coupled to receive and synchronize asynchronous pulses to a synchronous clock signal. A shift register is responsive to the asynchronous pulses to sequentially enable individual ones of the channels. In the case of a two-channel system, the shift register is a bistable device which enables the channels alternately.

Abstract: A read write head for magnetic recording on a magnetic media includes a core having a gap with confronting surfaces. To increase the magnetic saturation properties of the head, one of the confronting surfaces is covered with a layer of material having a higher magnetic permeability than the material making up the core. An additional surface of the core is also covered with the higher magnetic permeability material to prevent the flux lines from fringing into the atmosphere at the joint. The two layers of material form an integral layer of the second higher permeability magnetic material.

Abstract: An enclosed slurry dispensing system employs a sealed pressurized reservoir for supplying slurry through a bypass chamber to a dispensing nozzle. Excess slurry is bypassed through the bypass chamber to an intermediate chamber. Slurry is allowed to return to the reservoir through a normally-closed check valve, closed by the higher pressure of the reservoir. The system is purged by opening the reservoir to the atmosphere, creating a sub-atmospheric pressure in the bypass chamber. Air is admitted through the nozzle to purge the nozzle of slurry. At the same time, the check valve opens and excess slurry returns to the reservoir from the intermediate chamber.

Abstract: An apparatus for testing the surface properties of a material is disclosed. The apparatus includes an indentor which is suspended above the surface of a sample and dropped onto the sample. Several testing methods are also disclosed. Surface toughness is measured by dropping the indentor from a variable height and inspecting the surface for failure. Thin film strength is tested by making several drops from various heights and inspecting the surface for flaking of the layer. In addition, damping capacity can be measured by comparing the kinetic energy of the resulting from the drop of the indentor to the strain energy measured by a probe on the opposing surface of the sample.

Abstract: A data storage system has a plurality of individual data storage units, each of which can undergo unpredictable independent failure. By dividing data blocks to be stored therein into a number of sub-blocks one or more less than the number of data storage units and creating a redundant data sub-block of the type permitting reconstruction of any one sub-block of data using the remaining sub-blocks and the redundent sub-blocks, and then storing each of the data sub-blocks and the redundant sub-block on a different one of the data storage units, it is possible to reconstruct any one failed data sub-block of a related group using the other sub-blocks. It is necessary to be able to detect the failure of the sub-block, and the preferred way is by a multibit error detection code appended to each sub-block, or by failure sensed within and by an individual data storage unit.

Abstract: Certain stored program digital computer systems employ a single central memory to which requests are made for individual instruction words stored within it. Certain types of these memories employ address queues in which requests may be temporarily stored when requests come in more rapidly than the central memory can service them. A write valid memory records each central memory request and provides a status signal which can be used to prevent placing of a further request for the word at an address in the queue.

Abstract: Provided is a circuit for removing an unwanted temporal portion of an incoming signal and for differentiating that signal with respect to a reference voltage level. It includes an input for receiving the incoming signal current through an input capacitor, a differential amplifier for converting input charging current into a voltage with respect to a reference voltage, and a charging capacitor for holding a voltage level representative of the charging current supplied to the differential amplifier during times when the unwanted input signal portion is to be removed from the circuit's output. A current sink and source provides a reset period voltage charge to the input capacitor during times when the unwanted portion is to be removed from the outgoing signal. A switch responds to a reset signal immediately preceding or on the occurrence of the unwanted signal portion.

Abstract: A dual channel readback recovery circuit includes a high resolution channel and a low resolution channel and a data latch. A logical filter in one or both channels rejects signals that are followed by other signals if they are spaced apart less than the rejection time interval allowed by the code used. Polarity qualifying logic rejects signals in the channel that are not matched in polarity.

Abstract: A phase comparator generates a reference pulse equal in duration to one bit cell, and a variable pulse having a duration representative of the duration and time displacement of the leading edge of a data pulse from the center of the bit cell. The phase comparator includes two D-type flip-flops arranged so that the variable pulse is initiated by the leading edge of the data pulse in the one bit cell, the reference pulse is initiated by the edge of the clock pulse at the end of the one bit cell, and both pulses are terminated by the edge of the clock pulse at the end of the next bit cell. Hence, only clock edges at the bounds of the bit cell affect the pulse durations and the apparatus is insensitive to clock asymmetry.

Abstract: A vent cap has a long, narrow air communication passage covering the vent outlet of a sealed disk drive. The passage reduces diffusion of water vapor into the disk drive.

Abstract: A probe head for vertical recording includes a U-shaped member partially surrounding the probe and a coil supported by the U-shaped member. When the coil is energized, flux from the probe is focused to the region between the legs of the U-shaped member to greatly increase flux gradient during a write operation.

Abstract: This invention provides a structure for damping longitudinal vibrations in an apparatus which moves longitudinally.It employs, in a longitudinally moveable body, a structural element, slotted in the longitudinal direction, so that said structural element has relatively rigid upper and lower portions and relatively flexible flextures at the slot ends. A layer of elastomeric material covers a side of said element and a stiffening plate covers said elastomeric layer.

Abstract: A bias magnet for a bubble memory device is comprised of a single material low permeability magnet contoured to enhance the magnetic field in the central area of the magnet and is adapted to be slightly larger than the bubble memory chip and in thermal contact therewith, the entire bubble memory chip and bias magnet structure to be surrounded by the rotating magnetic field drive coil structure.

Abstract: A high velocity seek deceleration technique is disclosed for seek operations of disk drives wherein measured time per track is compared to a predetermined time per track in a memory as indexed by number of tracks to end of seek determines an error value which adjusts a deceleration amplifier. The gain of digital output to the amplifier is adjusted depending on the number of tracks to end of seek, the higher the number, the higher the gain. Further, a variable bandwidth filter is employed to increase bandwidth as velocity decreases.

Abstract: A gas laser optical recording apparatus having a write beam deflected from the optical path taken by the read beams by an acoustic optical modulator. In one embodiment the write beam is time-shared between the read optical path and the write optical path. In this embodiment an attenuator is placed in the read optical path to reduce the power of the laser beam from write power to read power. In a second embodiment 5 percent of the power is allowed to remain in the read optical path and the write beam is deflected between a beam stop and the write optical path as required.

Abstract: A vertical recording head includes a W-shaped core, a substrate carrying a thin film probe supported in one slot of the core, and a shield coil wound in the slots to hold the substrate and assemblage together. A non-magnetic cap forms the surface of the head over the cap, with the arrangement being such that the probe extends through the cap so the magnetic gap is as small as possible.

Abstract: A fan is disclosed that contains cut-outs that reduce the noise levels. The fan is used to cool circuit boards.

Abstract: A circuit means for detecting data errors in VLSI processing circuits at the earliest point such an error occurs in the processing stream or (in different modes) at any selected point therein, and for providing the prior operands and faulty (intermediate) output data together with an indication of what is wrong with the data. Described are registers and/or means for controlling the mode of the circuitry, error detection means (being, for example, parity check circuits), and an output means for providing the output in an organized way responsive to the controlling means and the output of the error detecton means. The method of using such a circuit is inherent in the disclosure.

Abstract: A method for polling headphones of a passive tv audience meter system. Tv audience members wear headphones by which they may receive the audio portion of the tv programs. The headphones are enabled to receive the audio for a short time by periodic polls transmitted by a tv audience meter. The headphones in turn acknowledge to the polls to indicate to the meter which members of the audience are watching tv. The method uses short and long period polls in conjunction with a timer whose period is shorter than the long period poll. The long period poll permits activation of headphone but also prevents adequate audio reception until the headphone acknowledges the poll. The short period poll is entered in response to the receipt of an acknowledgement and permits uninterrupted audio.

Abstract: A backup material for small bore drilling in hard .[.crystalline.]. materials, such as multilayer circuit boards containing polyimide/glass, polyimide kevlar or modified epoxy BT/glass, includes at least one layer of hard crystalline material. Standard LCOA material with an additional layer selected from the group comprising polyimides, fluorocarbons and high temperature polycarbonates has proven successful.