Abstract: A tape cartridge or other physical volume includes a housing configured to accommodate magnetic data storage media, such as a reel of magnetic tape. A magnetic field detector is coupled to the housing for indicating whether the housing has been exposed to a magnetic field of sufficient intensity to corrupt or bulk erase the magnetic media. In a first embodiment, the detector is implemented as a magnetic media element having a predefined pattern of magnetic domains recorded thereon. In a second embodiment, the detector is implemented with a magnetic film element having a predefined pattern of magnetic domains recorded thereon and a polarizing filter stacked on top of the magnetic film element to polarize light incident upon the magnetic film element. Based on the Kerr effect, light incident upon the magnetic domains will undergo a shift in polarization angle before being reflected back to the polarizing filter. Erasure or alteration of the magnetic domains will modify the polarization shift.

Abstract: A load short-circuit state detection circuit has a driver including X and Y terminals between which an inductive load is connected and receiving drive signals. The detection circuit further includes a first transistor whose base is connected to the X terminal and whose collector is supplied with a voltage, a second transistor whose base is connected to the Y terminal and whose collector is also supplied with a voltage, a first constant current circuit connected to an emitter of the first transistor through a first resistor and a second constant current circuit connected to an emitter of the second transistor through a second resistor. A comparator is provided for comparing a voltage of a node between the first resistor and the first constant current circuit with a voltage of a node between the second resistor and the second constant current circuit.

Abstract: A random access semiconductor memory having an array of memory cells is provided with an internal test circuit for testing the contents of rows of stored test pattern data which are read from the array in units of data rows, each read from an entire row of cells of the array. The test circuit can be based on a set of transistors which are respectively coupled to the bit lines of the cell array, for detecting coincidence between the states of all of the bits of a data row that is read out, or coincidence between the states of a predetermined set of the row bits.

Abstract: A storage apparatus which performs writing and reading of data on a magnetic tape by the helical scan method using a rotary head, in particular one suited to use with a large-sized host computer, which storage apparatus includes mainly a storage control unit connected to the host computer and a drive unit for reading from and writing on the magnetic tape. System areas are formed on the magnetic tapes, which system areas have tables which include management information relating to the magnetic tapes themselves and able to be renewed by the storage control unit. By using these tables, the magnetic tapes can be easily accessed at a high speed, diagnosed as to trouble, and managed in data blocks.

Abstract: Apparatus for measuring hysteretic properties of thin film recording disks is provided which comprises a magnetic field generator for magnetizing a spot on a piece of magnetic material to be tested. The magnetized spot is moved past a stationary Hall effect sensor which detects the magnetic flux being emitted from the magnetized spot. The process of magnetizing and detecting the flux emitted from the same spot is repeated at different magnetization levels to provide a set of automatic measurements that are recorded in a memory of a controller processor. An analysis of the recorded data permits the automatic computation of residual flux, remanent coercivity, switching field distribution as well as other hysteretic properties.

Abstract: A magnetic head tester has a popcorn noise detector for discriminating internally generated popcorn noise events from externally generated noise events. The popcorn noise detector includes a discriminator which receives the magnetic head output signal from the head and generates a comparator pulse for each popcorn noise event detected. A counter counts the number of pulses output from the detector. The discriminator includes a retriggerable noise detection gate circuit for producing a noise detection gate signal when triggered by a comparator pulse. The discriminator responds to a single comparator pulse during the gate period by indicating a popcorn noise event at the output of the discriminator. The discriminator responds to a plurality of comparator pulses during the gate period by indicating that no popcorn noise event has occurred.

Abstract: Techniques for certifying recording sites (bit sites) on magnetic recording disks wherein test recording patterns are recorded along disk tracks: first in an analog mode, then in a digital mode; concluding in a full digital test that simulates customer operation.

Abstract: A magnetization characteristic measurement device includes a differential magnetic head, a signal generator for exciting the differential magnetic head with a low frequency signal, a magnetic head moving device for moving the differential magnetic head to a predetermined measuring position, a measured data converting device for sampling the differential output voltages from the magnetic head when it is positioned at the predetermined position and for converting the sampled values into digital values, and a measured data analyzing device for sequentially storing the obtained digital values and for calculating the magnetizing characteristics. The structure allows for simple and easy measurement of magnetization characteristics of magnetic thin films attached to a magnetic printing, magnetic tape, etc. by simply setting the magnetic thin film at a position. The result of the measurement is displayed on a display screen or indicated using a buzzing sound to thereby reduce inspection steps.

Abstract: A magnetic head characteristic measuring device for determining the recording and reproduction efficiencies of a magnetic head, which uses an MR block consisting of plural parallel magnetoresistive elements disposed on opposite sides of a reference plane aligned with the center of the gap of the magnetic head. The MR elements detect a change in the vertical component of the magnetic field caused by a change in a leakage magnetic field generated in the gap, to gauge the recording efficiency of the head. The measuring device also includes a further MR element or other conductor capable of generating a test magnetic field when supplied with a current. When this test magnetic field is being generated, a measurement of the response of the magnetic head is taken in order to gauge the reproduction efficiency of the same.

Abstract: The manufacture of digital magnetic recording discs for computer disc drives requires the monitoring and control of the M-H hysteresis loop properties of the magnetic film deposited on the disc substrate. Several methods exist for measuring this M-H hysteresis loop, but they all have serious disadvantages. One method consists of cutting samples and measuring them with a vibrating sample magnetometer. This is a destructive test and requires a lot of time per sample. Another method uses the Kerr-rotation of polarized light. However, it samples only the mangetization of the surface and cannot determine the magnetic thickness of the film. A third method magnetizes the entire disc and samples a large region along a diameter. This method cannot distinguish between the top and bottom films of the disc, and cannot resolve circumferential variations of th M-H loop properties.

Abstract: A test fixture apparatus for testing drives of magnetic recording media; the apparatus being adapted to simulate magnetic media for insertion within a magnetic recording drive. The test fixture apparatus includes a structure formed with exterior dimensions approximating those of the magnetic media; one or more conductors positioned to be in close proximity to the gap or gaps of the magnetic recording head within the drive when the test fixture apparatus is inserted; signal detection and driver circuitry to drive the conductor or conductors in order to simulate readback flux reversals and to check write characteristics of the drive; and means to simulate index pulses for flexible disk applications. A magnetic data cartridge application is also included as an alternative embodiment.

Abstract: A magnetoelectric conversion element comprises a magnetoresistive effect material having a closed domain structure, a pair of contacts for supply of current flowing through the magnetoresistive effect material, and a bias electrode disposed between the contacts for biasing the direction of the current flow. The bias electrode is disposed so that the respective angles of intersection between the directions of current flow through different magnetic domains of the magnetoresistive effect material biased by the bias electrode and the directions of spontaneous magnetization biased by an external magnetic field are both increased or decreased.

Abstract: Disclosed herein is a method of testing a magnetic bubble device which guarantees allowable variation ranges for a variety of signal components of input signals applied to a magnetic bubble element when the magnetic bubble device is to be energized. A variety of signal components are varied in a testing cycle for writing, reading and collating information, whereby a plurality of combinations of the variety of signal components are obtained. The obtained input signals are continuously applied to the bubble element to effect the test.

Abstract: The specification describes a magnetic bubble device which incorporates a Z coil for providing a test magnetic field in addition to the usually provided bias field. In order to reduce package size the Z coil comprises at least one printed coil 17 formed on a substrate 15. The substrate 15 may be a flexible substrate such as polyimide film which is provided as a flap on a chip connection substrate formed from the same film, the flap folding over to lie parallel with the chip connection substrate.The invention enables a Z coil to be provided within a package without unduly increasing package height and provides an additional advantage that the substrate which supports the Z coil may be used to protect the magnetic bubble device chip.

Abstract: A magnetoresistant transducer for reading data present on the tracks of a multitrack magnetic carrier, comprises at least one magnetoresistant element perpendicular to the direction of travel of the data, and first and second magnetic screening means situated at either side of the element.The magnetoresistant transducer comprises deflecting means for deflecting the magnetic field generated by the current flowing through the element. The deflecting means are situated between the latter and the first and second screening means to intercept and deflect the magnetic field lines transmitted by the data items on the track. The deflecting means includes a plurality of mutually parallel thin magnetic blades separated from each other by thin non-magnetic laminations the thickness of which is such that the magnetic coupling between two adjacent laminations is weak. The laminations and magnetoresistances are of anisotropic material and have their axes of easy and difficult magnetization parallel to each other.

Abstract: The disclosure is of a method and system for scanning all of the cells of a dynamic memory at selected increasing time intervals. The apparatus includes first and second counters coupled to a comparator, the output of which triggers the operation of the scanning apparatus.When the system is turned on, the count in both counters is the same, and a signal appears at the output of the comparator to trigger the scanner. If no error appears in the memory, the first counter is incremented by a selected first count, and then the second counter is incremented from zero until its count equals that in the first counter, and, again, an output from the comparator triggers the scanner. Again, if no error appears in the memory, the first counter is incremented by a second greater count, which represents a larger time interval, and the second counter is incremented from zero until its count equals that entered in the first counter, and the comparator again energizes the scanner.

Abstract: A coil arrangement for testing magnetically operative devices comprising means for mounting a magnetically operative device to be tested by an external magnetic field; first and second coil means disposed symmetrically with respect to the place of the device, the coil means functioning to produce an external magnetic field for testing the device; characterized in that the first coil means is embedded within a metallic electrically conductive body for confining the magnetic field lines to a predetermined region.

Abstract: Disclosed is a method and apparatus for digital implementation and closed loop feedback of magnetic field waveforms utilizing three channels of a four channel incrementally programmable voltage source to drive field coils in each of three spatial axes, respectively. A fourth channel is utilized for signal conditioning of an output signal from a magnetic bubble memory undergoing test by injecting inverted noise to maximize the signal-to-noise ratio.

Abstract: Machine for testing planar magnetic film with magnetic bubbles and which comprises a testing device and a magnetic head, wherein the magnetic head incorporates two polarization coils in the Helmholtz position and whereof the common axis is normal to the plane of the magnetic film and two flat coils whose axes are perpendicular to one another and parallel to the plane of the magnetic film, the first of the polarization coils being arranged within the flat coils which are themselves arranged one within the other and on the same side of the magnetic film, while the test device and the second polarization coil are arranged on the other side of the magnetic film.

Abstract: The coercivity of materials that are capable of supporting single wall magnetic domains are measured by an expedient and accurate technique. This technique requires that the material be placed in a static magnetic field having a gradual spatial gradient. Finger shaped domains produced in the material are then modulated by introduction of an AC magnetic field. Coercivity is obtained by measuring the distance the finger domains move due to the AC field.

Abstract: A cateye-signal intercept detector for aligning a read-write head above a computer data storage disk. The detector used in conjunction with a standard disk having two adjacent cateye-type head alignment tracks thereon. The subject invention automates the detection of each intercept in the cateye-signal so that associated processing equipment responsive to the output signal produced can measure the read-write head disk alignment automatically.

Abstract: Method and apparatus for testing a magnetic bubble memory are disclosed wherein a most severe magnetic bubble domain arrangement which fully causes the ununiformity of magnetic interaction between magnetic bubble domains is experimentally determined, and a basic pattern [P] and a test information pattern determining an arrangement of the basic patterns [P] and complementary patterns [P] thereof for realizing that magnetic bubble domain arrangement are stored in memory units, respectively, and the basic patterns [P] and the complementary patterns [P] are sequentially read out in accordance with the test information pattern to generate magnetic bubble domain trains in a storage area of the magnetic bubble memory.

Abstract: A method of testing a magnetic bubble device which includes an integral magnetic shield is provided for setting the magnetization of the bias field thereof, in which a leakage magnetic field is induced in the shield of the device which is superimposed on the usual bias magnetic field for changing its magnetization.

Abstract: A method and an apparatus for characterizing magnetic materials especially LPE garnet films for magnetic bubble memory applications are described. The method and apparatus comprises in the first embodiment passing monochromatic linearly polarized light through a magnetic film, under no applied external field (Ha=0) with a randomly oriented stripe domain structure to produce a single diffraction grating, then (1) the angle of the first order diffracted beam is deduced by directly comparing the currents produced by a linear position photodetector and an ordinary intensity photodetector and (2) next a magnetic field (Ha) is applied normal to the surface of the film and the field is increased until intensity of the second order diffraction beam is maximized. In the second embodiment of the method so that higher signals can be detected for the first order diffracted beam, the film is magnetized so that the stripe domain configuration is parallel and the foregoing steps followed.

Abstract: Method and apparatus for testing and setting the field strength of permanent magnets in a magnetic bubble domain chip module, wherein the final molded module is formed to contain a pair of longitudinal slots which run through the module on opposite sides thereof. The module is inserted, via said slots, onto conducting members of a magnetic bubble module testing apparatus. The conducting members effectively provide one turn coils on each side of the module. Current is induced in these coils in such a way as to either add to or subtract from the bias field provided for the magnetic bubble domain chip by the permanent magnets of the module. The module is tested to determine the upper and lower operating levels of the bias field for effective operation of the chip, and the device is remagnetized to set the bias field of the module in the center, or optimal point, of the bias margin.

Abstract: A wafer indexing and mapping system is useful for precisely locating artifacts, defects, and fabricated structural components on a wafer. A permanent micrometer grid pattern is applied to the backside of the wafer, for example, a transparent bubble wafer. The grid pattern forms an array of uniform size cells, for example, 40 unit cells wide by 40 unit cells long. Each unit cell is divided into smaller units on each side. Each cell contains a coding or indexing system to identify the row and column of the cell in the grid pattern. The grid pattern contains orientation bars which identify orientation with respect to particular wafer reference lines. The simultaneous viewing of the wafer and the grid pattern permits an accurate permanent mapping of the artifacts, defects, and fabricated structural components on the wafer, as well as on the individual small chips formed by dicing the wafer.

Abstract: A magnetic orientation sensor for magnetic recording media includes a transducer that writes a magnetic pattern on the recording medium and then reads it back. The reading is taken a number of times at a given location but with the magnetic flux traveling in various directions. The strength of the readback signal is used to interpret the magnetic properties of the medium, in particular a direction of orientation which is the preferred or strongest magnetic conductor. The transducer and the medium are stationary with respect to one another at each measurement. The transducer or magnetic head consists of a circular or ring-type structure having a rotating center spindle having a longitudinal bar of magnetic conductive material on the face thereof to create a magnetic field of varying orientation during the writing and reading process.