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: 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: 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 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: A decoder for the 2,7 variable length code. A four-bit shift register sliding block decoder detects the presence of the code's four-bit ending sequence and provides decoded binary output. The decoder has only a three-bit binary error propagation.

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 read channel for an optical recorder. Data is recorded on the media in a fixed block code. The data is read and the location of the holes within a symbol are determined for the odd and even symbol positions separately. The location of the hole is determined for an odd or an even hole by using two sample and hold cells to hold the signal value received at a symbol position and compare it to the signal value received at a previous position. If the comparison results in a new higher valued signal being found, the output of the comparator changes. If the output of the comparator changes, the address of the change is recorded. The last such change denotes the location of the symbol position having the highest signal value, which is the address of the hole. The address of the holes, even and odd, are used to directly convert from the fixed block code to binary. Two symbols convert to 8 binary bits.

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.

Abstract: A calibration standard simulates predetermined flying characteristics of a magnetic head for calibrating flying height testers. The standard comprises a substrate having a reflective layer supported thereon. A transparent layer is disposed over the reflective layer so that the reflective layer is disposed at a predetermined angle to a surface of the transparent layer, the predetermined angle representative of a predetermined flying angle of a head over a disk, the transparent layer having a thickness representative of a predetermined flying height of a head over a disk. A process for manufacturing and calibrating the calibration standard is also described.

Abstract: A channel identifying rolling bar code, transmitted with a television broadcast signal, is displayed at a selected location on the receiving television screen. An apparatus is secured to the television set to view the rolling bar code to identify the channel being transmitted and process that information as necessary to detect the periods of time that different channels are received by the particular set. That information is stored in an internal memory for eventual use by a central processor.

Abstract: A slide lock mechanism for restraining movement of the carriage of a disk drive comprises a rod slideably supported by the disk drive housing for movement between two rest positions. A lock pin, fastened to a shaft engaging the rod, is moveable between a lock and unlock position to bias a pin, fastened to the carriage, against a stop when the rod is in one of its rest positions. An over-center spring, fastened to the housing and rod biases the rod to its two rest positions.

Abstract: A dual channel read recovery system having a high resolution channel and a low resolution channel and logic for recovering digital information from the high and low resolution signals from the channels, is improved by the inclusion of a variable delay in the low resolution channel. The variable delay is responsive to the high and low resolution signals to more closely match the delays in both channels.

Abstract: A bus contention circuit, is employed for each unit of a system capable of seizing use of a bus, wherein the units are arranged in a priority order. Priority resolution is accomplished by registering a request to seize use of the bus from any unit where either (1) no other requests are so registered or (2) the requesting unit is of lower priority than a unit whose request is already registered. When the bus becomes available for use, use is allocated to the unit with highest priority whose request is already registered.

Abstract: A desired feature of deposition material is produced on a substrate by forming an adhesion inhibitor on the substrate in a pattern whose inner edges are adjacent the bounds of the feature being produced. A seedlayer is deposited over the adhesion inhibitor and exposed portions of the substrate, and a mask is formed over the seedlayer adjacent the edges of the adhesion inhibitor, the inner edges of the mask defining the feature being produced. A deposition material is deposited over the exposed seedlayer, and the mask is removed. Unwanted portions of the seedlayer and deposition layer are removed by mechanically lifting off. The adhesion inhibitor serves to inhibit the bonding of the seedlayer to the substrate sufficiently to enable the mechanical lift-off. The adhesion inhibitor is removed, either by lifting off with the seedlayer and deposition layer, or subsequently.

Abstract: An overlapped document detector for a document handling apparatus comprises an air knife in the primary document path to separate overlapped documents and forward them along separate ones of two secondary paths. Optical detectors focused on each secondary path, detects documents to detect an overlapped condition. A vacuum is created to maintain the documents in their respective secondary paths for detection purposes.

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.