Abstract: A magnetic head and disk tester provides accurate positioning of a magnetic read-write head over a magnetic disk by means of a coarse positioning mechanism and a fine positioning mechanism. The coarse positioning mechanism includes a stepper motor, a lead screw, a nut, rear sliders and a housing. The fine positioning mechanism includes a piezoelectric actuator, slides and a carriage. The positioning displacements are along a linear axis, which lies on a horizontal plane. The carriage is connected to the housing via the fine positioning mechanism, which then moves the carriage with respect to the housing. Two pairs of linear encoders are mounted on the carriage about the axis and measure the position of the magnetic read-write head with respect to the magnetic disk. Each pair is mounted such that the pairs lie in separate horizontal planes.

Abstract: A shroud of suitable shape is provided about the spindle and disk(s) of a spinstand. The shroud operates to reduce or eliminate air flow at the top and bottom surfaces of the disk(s) and limits the air volume moved by the rotating disk(s). The shroud also directs the air in a circular path around the spindle center. As a result, vortexes in the air surrounding the disks are significantly reduced, thereby decreasing the vibrations of the disk(s) and the heads and decreasing track misregistration. The shroud also reduces the heat exchange between the ambient air and the magnetic disk(s), which in turn reduces the thermal expansion of the disk(s) and thus decreases the track misregistration further. The shroud also provides electromagnetic shielding for the disk(s) and head(s) installed on the spinstand and thus increases the quality of the signal read from the magnetic disk(s).

Abstract: A head-disk interface tester for magnetic recording disk drives uses a rotary voice coil motor (VCM) actuator and a rotating laser beam that rotates with the actuator to accurately move the head to the desired position and with the desired velocity. A diode laser is located on the rotating actuator and directs a laser beam through the pivot axis of the actuator. The laser beam is received by a linear position detector. The detector provides position data which is used by control circuitry to move the actuator to the position determined by the user or according to a velocity determined by the user. The rotary VCM actuator is mounted on an adjustable stage that allows the height of the actuator to be varied, as well as the distance between the actuator pivot axis and the spindle motor rotation axis to be varied.

Abstract: A shroud of suitable shape is provided about the spindle and disk(s) of a spinstand. In some forms, a shell is disposed between the disk locus and the shroud. The shroud (and/or shell) operates to reduce or eliminate air flow at the top and bottom surfaces of the disk(s) and limits the air volume moved by the rotating disk(s). The shroud (and/or shell) also directs the air in a circular path around the spindle center. As a result, vortexes in the air surrounding the disks are significantly reduced, thereby decreasing the vibrations of the disk(s) and the heads and decreasing track misregistration. The shroud (and/or shell) also reduces the heat exchange between the ambient air and the magnetic disk(s), which in turn reduces the thermal expansion of the disk(s) and thus decreases the track misregistration further. The shroud (and/or shell) also provides electromagnetic shielding for the disk(s) and head(s) installed on the spinstand and thus increases the quality of the signal read from the magnetic disk(s).

Abstract: Obtaining fast dipole size estimation with less influence of noise by using a regional dipole model. An artificial neural network section 30 executes regional dipole size estimation using a neural network having coupling coefficients representing coupling states among as plurality of units and thresholds thereof.

Abstract: A method and apparatus for start-stop testing magnetic heads and hard disks in real disk-drive environment is provided. The tester has essentially the same dimensions as a conventional disk drive so that rotation of the disk pack inside the tester housing generates the same aerodynamic conditions as in a real disk drive. An accurate head positioning system, the operation of which does not depend on the deterioration of the magnetic conditions of the head and disk, is located inside the tester housing, and the friction and sticking forces can be measured till the moment of physical crash inside the housing. An essential advantage of the tester of the invention in that the measurement and positioning systems are combined into a single unit. The aforementioned combined system is based on the use of a Hall-effect sensor attached to the voice coil of the type used in the disk drive.

Abstract: A spinstand head-loading mechanism of a magnetic tester includes a protector bar and a lift arm which control the loading and unloading operations of a magnetic head, as part of a head-gimbal assembly, with respect to a magnetic disk. A series of actuators control the engagement and disengagement of protector bar and lift arm with a head-gimbal assembly that includes read/write elements as part of a slider. The protector bar is driven in a Y-axis direction by an actuator, while the head-gimbal assembly is disposed in an X-axis direction, orthogonally to the Y-axis. The lift arm is also driven in the Y-axis direction by an actuator, but is also driven in a Z-axis direction by a different actuator. Before testing, the head of the head-gimbal assembly is loaded onto a magnetic disk. To accomplish this, the head-gimbal assembly is initially installed on the head-loading mechanism.

Abstract: A method of varying the capacity of a multi-platter hard disk drive, having a plurality of head/disk combinations, during a manufacturing process includes scanning the overall disk surfaces to detect defects. If the number of defects detected on a disk surface exceeds a design specification number, the head/disk combination having the disk surface is determined to be defective. Then, the use of the defective head/disk combination is avoided, to thereby vary the capacity of the hard disk drive.

Abstract: A method of analyzing defects in a magnetic thin film is provided. A magnetic field is applied to the magnetic thin film. The magnetization of the magnetic thin film is measured over a range of different field strengths. A value representative of a magnetic hardness coefficient is calculated for the magnetic thin film from the magnetizations measured. The calculated value is compared with a reference value. Defect information is determined in dependence upon the comparison made.

Abstract: An asymmetry measuring apparatus is provided which comprises: dividing means for dividing read data output from a read data generator in data storing means; a DC level converter for converting the duty ratio of a signal divided by the dividing means to a DC voltage level; and DC voltage measuring means for measuring the output voltage of the DC level converter. By virtue of the above construction, the asymmetry measuring apparatus does not need a lot of time for measurement, causes no significant measurement error, is suitable for mass production, and creates no quantization error at the time of counting of a reference clock in time measurement.

Abstract: A method for measuring the width of an erase band located adjacent to a test track containing a periodic signal at a specified frequency is disclosed. For each position of a read head as it incrementally traverses the erase band and test track, an information signal is read, and a signal level data point is stored which represents the amplitude of the fundamental frequency obtained from a Fourier transform of the information signal. In addition, a media noise level data point is stored which represents an integration of a noise power spectrum obtained from the Fourier spectrum of the information signal over a predetermined frequency range. Once the signal and media noise level data points are obtained, the edge of the test track is approximated by determining from the signal level data points a point at which the amplitude of the stored signal level data points departs from an otherwise substantially constant background noise level.

Abstract: Methods and apparatus for testing a magnetic disk and a read head are provided. A reference track is written on the magnetic disk. The read head is scanned laterally with respect to the reference track while the magnetic disk is rotating. The reference track is sensed with the read head as the read head is scanned across the reference track to produce a scanned read signal that is representative of disk and read head performance. The scanned read signal may be processed to provide parameters such as track average amplitude, signal-to-noise ratio, and pulse width of write transitions.

Abstract: A glide testing apparatus includes a motor assembly, a sensor element, a positioning assembly, and detection circuitry. The motor assembly rotates a magnetic disk about an axis. The sensor element produces a detection signal in response to disk surface characteristics. The positioning assembly positions the sensor element at selected radii from the axis of disk rotation, and the detection circuitry receives a signal from the sensor element to detect movement of the sensor element between a first zone on the disk and a second zone on the disk. Methods of distinguishing between two adjacent zones on a magnetic disk include rotating a magnetic disk about an axis and positioning a sensor element at selected radii from the axis of rotation.

Abstract: The contact tester of the present invention includes: a holding mechanism for holding a disk and rotating integrally with the disk, an arm driving for driving an arm which supports a slider, the slider is provided with a head for recording/reproducing information on/from the disk. In addition, a first vibration detection element for detecting contact between the slider and the disk is provided. Furthermore, a signal transmission for transmitting an output signal of the first vibration detection element and a signal analysis for analyzing the output signal transmitted via the signal transmission are provided, where the first vibration detection element is mounted at a position where a vibration of the arm is not detected.

Abstract: A disc certification process, apparatus and article of manufacture for improved testing efficiency employs a testing head having a write element and a read element supported adjacent a rotating disc recording surface. The write element has a width that defines a "wide" write track width of at least N times the read track width defined by the width of the read element, wherein N is an integer greater than 1. The write element writes a signal onto the recording surface of the disc during a first disc rotation, to define a first annular write track having a "wide" first write track width in the radial direction of the disc. Then, during a second rotation, the read element reads the signal written in a first reading track width defined within the "wide" first write track. Thereafter, the read element is stepped to another read position adjacent the first write track and the read element reads the signal written onto the recording surface in a second reading track width defined within the first write track.

Abstract: A method and apparatus are provided for detecting surface defects in a direct access storage device. Disk data readback sample values are converted to gain error values based upon an identified difference from predefined ideal data values. An error signal accumulator accumulates a summed value of error signals for a current sample and a predetermined number of past samples. Each sequential accumulator summed value is compared with a predetermined threshold value. An error output is generated responsive to each sequential accumulator summed value greater than or equal to the predetermined threshold value, the error output identifying the disk surface defect.

Abstract: Head disc interference is detected and analyzed using the standard deviation of read back signal frequency. First, the amount of longitudinal head oscillation affecting transducer read/write heads located in the hard drive is measured. Measuring the longitudinal head oscillation is achieved by determining the degree of frequency modulation associated with the read-back signal as compared with a constant frequency used to write the information. Second, this measured amount of oscillation is compared to a predefined threshold value. Finally, a head disc interference alarm is activated when the oscillation is greater than the defined threshold value.

Abstract: In the recorded magnetization state measurement method of this invention, a recorded magnetization pattern formed on a medium is first detected by a magnetic force microscope (MFM). An MFM output signal extractor then extracts a one-dimensional MFM output signal along the direction of recording at a prescribed MFM reproduction width from the recorded magnetization pattern detected by the magnetic force microscope. A waveform value analyzer then calculates as output reproduction the average value of amplitude of the MFM output signal extracted by the MFM output signal extractor and calculates as medium noise the standard deviation of amplitude of the MFM output signal.

Abstract: A method and apparatus for detecting and measuring head-disc interference, in a disc drive, for the purpose of taking preventative and corrective measures, to prevent disastrous head crashes and permanent data loss, is disclosed. The method and apparatus detect and measure the frequency modulation (FM) of a read back signal generated by longitudinal head oscillation, as a result of head-disc interference. The longitudinal head oscillation can be ascribed to the non-linear response of the air bearing supporting the head on the disk surface. The response exhibits a vibration frequency in the head in the 100 to 250 kHz range. The more severe the interference contact is, the higher the vibration amplitude which then leads to read signal frequency modulation (FM). A method and apparatus is described to detect the FM modulation and thereby to detect the severity of the head disk interference for proximity recording. A pre-written pattern on the disk can be read back to monitor for FM, and a modulation index, .beta.

Abstract: An improved fine positioning mechanism in a magnetic head/disk tester includes a primary position actuator and a primary body that supports a read/write head to be tested, and an auxiliary body and auxiliary actuator. Both actuators operate contemporaneously and in mutually opposite directions. The masses of both bodies and the stiffnesses of both actuators are selected so that a ratio of the stiffness of the actuator to the mass of the body in the primary system is equal to a ratio of the stiffness of the actuator to the mass in the auxiliary system. In addition, the masses of both bodies and the expansion coefficients of both actuators are selected so that a product of the mass of the body with the expansion coefficient of the actuator in the primary system is equal to a product of the mass of the body with the expansion coefficient of the actuator in the auxiliary system.

Abstract: A test data is written in an arbitrary point p on a non-linear characteristics portion of a hysteresis characteristics of a piezo actuator by a write head and the written test data is read out by an MR head using the point p as a reference to detect a maximum read-out voltage to thereby obtain a drive voltage of the piezo actuator corresponding thereto. From the drive voltage of the piezo actuator thus obtained, a position of the MR head whose offset is to be corrected is detected. In a magnetic disk certifier, the position of the MR head is corrected by applying the drive voltage corresponding to the maximum read-out voltage to the piezo actuator and the written test data is read out thereby. Thus, the position of the MR head on the piezo actuator becomes that of the write head when the offset correction value is detected and it becomes possible to correct the offset of the MR head with respect to the write head.

Abstract: A method and apparatus for loading and unloading a slider onto the surface of a substrate. The present invention includes a suspension assembly that supports a slider having an air bearing surface. The suspension assembly is coupled to a guide rod that is biased toward a first, second and third bearing. The guide rod remains in continuous contact with at least two bearings. Movement of the slider toward or away from the substrate surface is accomplished by changing the position of one or more of the bearings. In this manner, a set of pivot points acting upon the guide rod is varied as the slider is rotated toward or away from the disk surface such that the axis of rotation of the slider varies as the slider is rotated toward or away from the substrate surface. The loader is also configured to minimize the lateral movement of the slider along the surface of the substrate as the slider is loaded or unloaded from the substrate surface.

Abstract: A method is disclosed for calibrating a position error signal (PES) to overcome the problem of an amplitude signal that varies as a non-linear function of real displacement when the read transducer is positioned to either side of a null position where the PES equals zero. The amplitude signal and resulting PES is notably nonlinear while reading servo burst information with a Magneto-Resistive (MR) head which has nonlinear magnetic characteristics. The calibration according to this method may be performed at anytime without need for real displacement information from a servo track writer or any sort of special calibration track. The method involves positioning the MR head to a plurality of nominal partial track displacements on either side of the null position, measuring an open loop gain value for a particular frequency at each of the displacements, deriving the coefficients of a 3.sup.rd order polynomial "gain" curve that best fits the data, integrating the "gain" curve using the coefficients to obtain a 4.

Abstract: A data storage system that uses a magnetic head assembly having a write head and a read head mounted on a slider to write on and read from a disk. A portion of the coil of the write head is used as a wear sensor for detecting wear on the surface of the slider. A head IC monitors the coil voltage and, when it goes lower than a reference voltage, detects the occurrence of a fault in the write head due to excessive wear on the slider surface. In response to the detection of the fault in the write head by the head IC, a control driver prohibits a write operation and saves data already recorded on the disk.

Abstract: A system for magnetically evaluating magnetic data storage media includes a spindle for rotatably supporting magnetic disks, a read/write transducer, and an erasing transducer, both supported for radial movement relative to the disk. The read/write transducer records a sequence of magnetically isolated transitions. When sensing the sequence, the read/write transducer generates a fringing field signal which is low pass filtered and RMS processed to provide a voltage proportional to the remanence-thickness product. The erasing transducer is a ring head transducer having a substantially larger gap and transducer/disk spacing as compared to an aerodynamically supported transducer. Consequently a Hall effect probe is positionable within the gap to directly measure the magnetic intensities of erase fields.

Abstract: A fastening portion 1a of a plate spring 1 of a head unit H supported by a support member 12 and an arm portion 1d is pressed by a pressurizing pin 22a to impart the same displacement to a slider 4 as a Z-height when the head unit is mounted to an apparatus. In this condition, the inclination of the slider 4 is measured, and, further, the arm portion 1d is twisted by a tool 30 to correct deformation in the roll direction. Since the plate spring 1 is corrected in the same condition as when the unit is mounted to the apparatus, an accurate correcting operation is conducted.

Abstract: A magnetic head loading mechanism for loading two magnetic heads 2(A) and 2(B), each of which is attached at a tip of respective one of supporting arms 3 and 3, onto a surface of a magnetic disc 1 to be tested being rotated with high rotation speed, comprising: two adopters 71(A) and 71(B), on which are fixed the supporting arms 3 and 3 in a detachable manner; two head position adjusting mechanisms 74(A) and 74(B) for rotating the adopters 71(A) and 71(B) so as to bring the supporting arms 3 and 3 into either an escaping condition in which they are far away from the surfaces of the magnetic disc 1 each by a rotation angle of 90.degree.

Abstract: Inserting operational data onto a magnetic disk allows information to be transferred from a servowriter station to a verifier station. This operational data allows disk specific operational data to follow the disk without separate means for attaching data to each disk. The servowriters, which cannot write information to disks at the data sector frequency, inserts the operational data into selected greycodes in the servo sectors. When the disks are verified, the operational data may be moved from the servo sectors to the data sector in the Z-tracks for more permanent storage.

Abstract: Functional devices for inspecting disks are arranged around a turntable at equal spacings of angle 2n.pi./(n+m) in the order of the operations they perform. The turntable is rotated both in forward direction by angle 2n.pi./(n+m) and in reverse direction by angle 2m.pi./(n+m) such that the total angle of rotations in forward direction is equal to that of rotations in reverse direction when the necessary operations have completed without causing the turntable to rotate fully once.

Abstract: An acoustic emission technique and apparatus that determines the take-off velocity of a slider based upon a quantitative measurement of slider velocity without internal access to the file. The system includes a vibration detector for detecting contact energy, and for producing an output signal; and a logic circuit coupled to the vibration detector, for processing the output signal from the vibration detector to identify a slider take-off velocity. The slider take-off velocity is derived by multiplying lambda by the characteristic frequency, where lambda is the spacing between bumps in a circumferential direction. The output signal of the vibration detector disappears when the slider clears the landing zone. The vibration detector is attached to the actuator screw or other vibration transfer features accessible from outside the disk drive.

Abstract: A method and a system for fixing and positioning a headstack (100, 200, 300, 400) on a headstack tester by utilizing a vacuum chuck (105, 106, 208, 310). The vacuum chuck engages headstack. This engagement determines the exact position of the magnetic heads (24a, 24b . . . ) supported by the headstack with respect to the working surfaces (S1, S2, S3) of magnetic disks ((111a, 111b, 111c) of the disk pack of the tester.

Abstract: A method and apparatus for testing a magnetic head provided with at least one MR transducer. The method includes a step of applying a sense current varying with respect to time to the MR transducer element via input/output terminals of the MR transducer element, and a step of measuring a terminal voltage across the input/output terminals of the MR transducer element to check varying resistance characteristics of the MR transducer element with respect to the variation of the applied sense current.

Abstract: A disk certifier which analyzes a read signal generated from a disk of a hard disk drive. The read signal typically has a sinusoidal waveform with modulated peak amplitudes. The waveform is generally defined by the equation A.multidot.sin(wt).multidot.(1-m(t)), where the term m(t) is the amplitude modulation of the signal. The peak signal is provided to a phase lock loop circuit which generates a multiplier peak signal generally of the form sin(wt). The certifier includes a multiplier which multiplies the read signal by the multiplier read signal to provide a multiplied read signal described by the equation A/2.multidot.(1-cos 2(wt)).multidot.(1-m(t)). The multiplied read signal is filtered by a low pass filter which has a cut-off frequency Wc below w. The low pass filter provides a filtered multiplied read signal which is described by the equation A.multidot.(1-g(t)), wherein the term g(t) is the portion of m(t) with frequencies below Wc.

Abstract: The present invention relates to a method and apparatus for the measurement of defects in magnetic recording disks using a logarithmic amplifier. A magnetic head senses a magnetic field of a magnetic disk and creates a read signal having a varying amplitude. The test apparatus has a squarer which receives and squares the read signal. A logarithmic amplifier coupled to the squarer converts the squared signal to a logarithmic signal. The logarithmic signal is filtered by a first filter. A second filter coupled to the logarithmic amplifier provides an average of the peaks of the logarithmic signal. A digital-to-analog converter coupled to the second filter scales the output of the second filter. The test apparatus further comprises a comparator having a first input and a second input, where the first input is coupled to the first filter, and the second input is coupled to the digital-to-analog converter.

Abstract: An asperity height sensing head and method of using the same are disclosed. The head includes multiple magnetoresistive (MR) sensors carried by a first rail of a slider adjacent to the air bearing surface (ABS) and positioned a distance L.sub.p from each other. Asperity height estimating circuitry coupled to each of the multiple MR sensors detects a number N of the MR sensors which exhibit a change in resistance as a result of contact between the ABS and a first asperity on the surface of the disc. The asperity height estimating circuitry estimates the height H.sub.A of the first asperity as a function of the number N, as a function of the pitch angle .theta..sub.p , and as a function of the distance L.sub.p.

Abstract: An apparatus for testing and processing a magnetic disk. The apparatus comprises a spindle for rotatably supporting the disk about a spindle axis; a first read and/or write head; a second read and/or write head; a gliding head; and a burnishing head, where the heads are selectively positionable along parallel axes overlying the magnetic disk; and a controller for selectively driving said heads across the magnetic disk and for selectively rotating the spindle in first and second directions.

Abstract: An apparatus for testing magnetic heads that interact with magnetic disks includes a translational slide and a rotatable arm mounted to one end of the slide. The translational slide moves the rotatable arm in a longitudinal direction parallel to the surface of a magnetic disk. The arm rotates the magnetic head to different positions relative to data tracks on the disk. A second translational slide moves the magnetic head vertically above the disk to adjust the vertical position of the head. The three movements of the head, (1)horizontally across the disk, (2)rotationally by the arm, and (3)vertically relative to the disk surface are controlled by servomechanisms. A read/write amplifier circuit is connected to the head under test. The test apparatus is controlled by a computer that interfaces with circuitry connected to the servomechanisms.

Abstract: An apparatus for testing magnetic heads and disks comprises a phase locked loop (11) with a phase detector (13) formed by an analog-to-digital converter (40) and a digital-to-analog converter (50). A sine wave signal is supplied to an analog input of an ADC (40) and raw data pulses are supplied to the clock input the of ADC. A phase detector (13) detects deviations in the positions of raw data pulses from the zero crossings of the sine wave signal. A PLL (11) locks in the locations of the zero crossings of the sine wave signal and ADC samples constitute instantaneous values of a bit-shift distribution. These values are processed by a DSP (70). The resulting bit-shift distribution is generated during one disk revolution.

Abstract: A method for testing slider/disk contact in a disk drive is described. The disk drive comprises a rotating disk having tracks and a head mounted by an actuator for selective positioning of the head over any one of the tracks of the disk. The head includes a slider. The method comprises the steps of positioning the head at each of a preselected set of tracks, while at each one of the preselected set of tracks, rotating the disk of the disk drive at a preselected rotational velocity and using the head of the disk drive, at each track, to write a signal having a substantially uniform pattern on the disk as it rotates. Thereafter, rotating the disk at a fixed preselected rotational velocity, and while rotating at the fixed preselected rotational velocity, using the head to read back the signals written at each one of the preselected set of tracks. The read back signals are used to determine rotational velocities at which slider/disk contact occurs.

Abstract: A method and apparatus is provided for accelerating the wear of gas lubricated surfaces that operate in intermittent contact. The method includes the generation of ultrasonic sound in the gaseous atmosphere surrounding the interface, and the further directing, focusing, or concentrating of said ultrasonic sound to impinge upon the gas bearing inlet. This method is capable of more accurate interface lifetime predictions than conventional methods, since, in contrast with conventional methods, the medial gas bearing properties, environmental parameters, and structural support conditions, present during testing, are unchanged from those present during typical operation. The present invention will also enable the evaluation of the effects of magnetic disk drive component design changes, in terms of head disk interface lifetime, even when a majority of the wear occurs during normal device operation and not during device starting or stopping.

Abstract: A testing apparatus for detecting popcorn noise in magnetic heads comprises a fully integrated testing system which includes an analog circuit portion and a digital circuit portion. The analog circuit portion is implemented to interface with a magnetic head while the digital circuit portion is designed to store the testing sequence, analyze the testing data, control and execute the testing routines. The testing apparatus is designed for production environments where testing data are required instantaneously as feedback for production process monitoring.

Abstract: In a disk drive, the tendency of a flying head to physically engage a constant-speed data recording disk when the drive is operated at an altitude higher than the altitude at which the drive was manufactured is tested by. During manufacture of the drive, the constant disk speed is reduced to a lower speed that is a function of a mathematical relationship between the manufacturing altitude to the higher altitude. The invention then determines if the head in fact physically engages the disk at this lower speed. In an embodiment, this lower speed is calculated as a function of the ratio of the manufacturing altitude to the higher altitude. An embodiment of the invention provides a rotatable rigid magnetic recording disk and a magneto-resistive (MR) head that is generally stationary relative to the rotating disk.

Abstract: A magnetoresistive element is used to detect a surface roughness of an object, such as a magnetic recording medium, a photomask blank, a semiconductor wafer, and is assembled into a reproducing head which moves along a surface of the object and which can produce an electric signal related to the surface roughness. The reproducing head may be incorporated with a recording head into a head unit. The head unit can monitor a magnetic characteristic of the magnetic recording medium in addition to detection of the surface roughness, by recording a predetermined signal by the recording head and by reproducing the predetermined signal by the reproducing head.

Abstract: An electronic system for detecting flaws in the magnetic media of raw disks prior to assembly into disk drives which works in conjunction with an electro-mechanical apparatus that performs the functions of spinning the disk, impressing a sinusoidal signal onto the media of the spinning disk and subsequently reading back the signal from the spinning disk. The signal read from the disk is supplied as the electrical output of the electro-mechanical apparatus. The system includes a divider circuit to divide the read signal into two signal channels. An op amp based impedance matching circuit is connected to the output of the dividing circuit in each channel and matches the electrical impedance of the electro-mechanical apparatus with the impedance of the remainder of the electronic detection system. It passes the two signals through substantially unaltered.

Abstract: In a record medium checking device, a signal recorded on record medium is reproduced, then the absence of reproduced signal is detected. The device includes a reproducing means for reproducing the signal recorded on the record medium to output the reproduced signal, a discriminating means for comparing the reproduced signal with a reference signal to output a discriminating signal, a signal generating means for generating detecting clock pulses, and a counter to count the detecting clock pulses. The output of the counter is a check signal based on the discriminating signal.

Abstract: A method and apparatus (10, 410) for testing magnetic media read/write head components such as a head element bar (46) and a slider assembly (546). The component to be tested is held in a head bar holding assembly (44) or an alternate head holding assembly (544), and positioned with a head gross positioning assembly (18) or a head fine positioning assembly (16) over a localized portion (50) of a flexible magnetic medium (28) which is caused to spin in relation to a stabilizer plate (20) by a media spin motor (28). The localized portion (50) is deformed to bring the localized portion (50) of the flexible magnetic medium (28) into proximity with the component under test.

Abstract: Benzothiophenes and related compounds of the formula ##STR1## are estrogen agonists which are useful for treating prostatic and diseases, obesity and bone loss in male animals.

Abstract: A method and apparatus is disclosed or determining the remanent noise in a magnetic medium by DC saturation of a region thereof and measurement of the remaining DC magnetization. Conventional recording transducers may be used to determine the remanent noise. Upon determination, the remanent noise may then be compensated for in either or both of the record and playback modes for all varieties of magnetic media including, videotapes, cassette tapes, etc.

Abstract: To perform digital processing of cyclical waveform signals that include random noise with high accuracy and high reliability without being practically affected by the noise. This is a waveform signal processor into which cyclical waveform signals are input and which outputs corresponding signals. It samples a cyclical waveform signal a plurality of times and then, based upon the obtained sampling values, it performs a Fourier Transform for all the various cycles. Next, the phase angle of a pre-selected frequency component in the Fourier series is determined based upon the Fourier Transform. Then a sampling point at the same phase for all cycles is specified by using the phase angle as a reference. The average of the sampling values at the same phase is calculated and output.

Abstract: A method is described for testing for slider/disk contact in a disk drive comprising a rotating disk and a head mounted by an actuator for selective positioning of the head over the disk, the head having a slider, and a spindle motor for rotating the disk. The method comprises the steps of providing power to the spindle motor to cause rotation of the disk at a preselected rotational velocity corresponding to a rotational velocity designed for the disk during normal read/write operation, and thereafter withdrawing the power from the spindle motor such that the disk spins down to zero rotational velocity. While the disk spins down to zero rotational velocity, an acoustic coupling is formed between an acoustic emission sensor having an electric output and the spindle motor to provide first electric signals representative of acoustic emissions from the spindle motor, including acoustic emissions caused by slider/disk contact.