Abstract: A demodulator system for identifying the position of a transducer assembly over a disk of a direct access memory device. The demodulator identifies alias cases and uses information placed in the boundary between tracks to generates a more robust indication of the location of the transducer assembly.

Abstract: In a magnetic disk apparatus including a magnetic head and a magnetic disk medium having projections provided with a constant regularity, a rotating portion for driving the rotation of the magnetic disk medium is controlled by a control section in accordance with the regularity of the projections provided on the magnetic disk medium, a resonance frequency of the magnetic head and a relative speed of the magnetic disk medium to the magnetic head in order to prevent the resonance of the magnetic head from being caused by the projections of the magnetic disk medium. With such a construction, it is possible to realize the stabilization of floatation of the magnetic head in the magnetic disk apparatus, thereby providing a magnetic disk apparatus which has a low floating height and a high reliability.

Abstract: A circuit forming part of an arm electronics module installed on an actuator arm that measures the voltage across an MR head A control unit supplies a measurement enable signal that enables a measurement enable circuit. A current bias circuit, responsive to the control unit, supplies a bias current to the MR head. A common node in the circuit provides a voltage signal responsive to the voltage across the MR head, with an added diode V.sub.BE drop across an input transistor. A voltage measurement amplifier has an input node and an output node that supplies an output voltage reduced in voltage by one diode drop (V.sub.BE). An input switch, responsive to the measurement enable signal is coupled between the input node and the common node. An output switch, responsive to the measurement enable signal is coupled between the output node and an output terminal.

Abstract: Disclosed herein is a magnetic tape unit having a magnetic head for reading and writing data from and onto a magnetic tape. The magnetic tape is traveled in contact with the magnetic head during a read/write operation of the magnetic head. During a rest period where the read/write operation of the magnetic head is not performed, a reciprocating motion of the magnetic tape by a small distance is performed with a predetermined period. A temperature in the vicinity of the magnetic head is detected by a temperature sensor. The predetermined period is changed according to the temperature detected by the temperature sensor. Accordingly, the adhesion of the magnetic tape to the magnetic head can be well prevented irrespective of the temperature inside the tape unit.

Abstract: A disk drive preamplifier unit includes a serial interface circuit for receiving serially formatted control signals from an associated disk drive controller. The control signals contain several types of information, including head select, write current magnitude, bias for MR transducers, gain magnitude for a variable gain amplifier, and test and mode information. The preamplifier unit incorporates several test circuits in addition to the usual write unsafe detector circuit, and a multiplexer controlled by the mode control signals from the serial interface unit is used to select which test circuit or detector is coupled to a common test output terminal whose signals are coupled back to the controller for further processing.

Abstract: A hysteresis circuit for providing hysteresis for a degree of noise immunity when detecting zero-crossings of a hard disk drive. A comparator is used to detect the zero-crossings associated with one of the windings of the disk drive's spindle motor. When a zero-crossing is detected, the hysteresis circuit introduces a hysteresis voltage to one of the inputs to the comparator. A positive hysteresis voltage is applied when the slope of the back emf signal corresponding to the motor winding is negative. Conversely, a negative hysteresis voltage is applied when the back emf signal has a positive slope. The slope of the back emf signal is determined by a logic combination of the commutation signals used to commutate the spindle motor.

Abstract: A data recording disk drive for use in a portable, battery-powered computer has several power-save modes of operation. The power-save modes are entered after a computed time since the last data read or write command. The computed time to enter a power-save mode is based on the computer user's real-time workload and is thus continuously varying during operation of the disk drive. The disk drive detects the current user workload by calculating the frequency of disk drive accesses and based on this history determines which of a plurality of power-save modes is appropriate and when to enter a power-save mode. Each disk drive read or write access is detected and used to compute a current access frequency. The current access frequency is compared to a previously calculated and continuously updated threshold frequency. The threshold frequency is representative of the access pattern, e.g., uniform or sporadic, and is computed from equations that include adjustable gain factors.

Abstract: A method and apparatus for testing for mechanical defects in a disc drive during manufacturing test is disclosed. Resonances in the disc drive are excited by injecting a sinusoidal test signal of known magnitude and frequency into an incoming servo position error (SPE) signal in the servo loop to provide a modified SPE. While the test signal is injected, the modified SPE is sampled and filtered to characterize the test frequency in the modified SPE which is compared to a resultant frequency characterized in the incoming SPE. The presence of resonances in the disc drive structure will result in an increase in the gain of the loop as indicated by the characterized resonant frequencies from the incoming and modified SPE. When the gain exceeds predetermined criteria, an error flag is set indicative of a failure condition for the disc drive, enabling the disc drive to be removed from test for subsequent remedial actions.

Abstract: A magnetic recording tape cartridge having a rotatable lid member on a front face of the cartridge such as a video tape cassette which comprises an engaging member projecting from the lid member to the interior of the cartridge case, a movable locking member detouchably engaged with the engaging member of the lid member to lock the lid member in a closed position and to release the engagement of the locking member from the engaging member, and a throughhole defined to allow passage of a lock releasing pin of a recording/reproducing apparatus.

Abstract: A recording-reproducing apparatus, comprising first and second holding members and support member for supporting said first and second holding members, and for permitting said first holding member to move towards and away from said second holding member. The first holding member holds on one side thereof, a container member for containing a recording medium therein, and on an opposite side thereof, an adjusting member for adjusting the position of the recording medium. The second holding member holds a driving member for driving the recording medium.

Abstract: Any one of a number of heads of a cassette tape recorder of the automatic reverse type is selected by alternately bringing each of the magnetic heads into a position in which the magnetic head comes in contact with a magnetic tape, by pivoting a head lever in response to a movement of a plunger. The head lever has at least one magnetic head at each end thereof about the center of pivotal movement. A pinch roller is brought into a position in which the pinch roller on a pinch roller lever, comes in contact with the magnetic tape, by pivoting the pinch roller lever in response to the movement of the plunger.

Abstract: Playback, recording, and stop button plates are slidably mounted in parallel on a base plate. When pressed, the recording button plate engages the playback button plate so as to be locked to a recording position. A seesaw lever, which has a lock strip capable of engaging the playback button plate, is located in a plane across the sliding direction of the playback button plate and attached to the front wall of the base plate. An ejecting plate capable of engaging the stop button plate detects the difference between the displacement of the seesaw lever in the playback or recording mode and that in the stop mode. The stop button plate performs a stopping function without engaging the ejecting plate in the playback and recording modes, and engages the ejecting plate to perform cassette ejection in the stop mode.

Abstract: A repeat playback circuit device for use in a tape recorder in which the tape recorder is prevented from jumping again into a inter-music detection mode before the beginning of a desired segment of music is detected. During a normal play operation, pulses from an oscillator source are applied to the clock input of a counter while pulses indicative of the presence of a segment of music are applied to the clear input of the counter to thus prevent the counter from reaching a predetermined count. At the end of the segment of music, the pulses applied to the clear input of the counter are removed, whereupon the counter can then reach the predetermined count. When the counter does in fact reach the predetermined count, the tape recorder is set to the rewind mode where it remains until a blank segment is detected, at which time the tape recorder is placed in the play mode. The counter is set to be ready to detect a blank portion on the tape at the beginning of a segment of music when in the play mode.

Abstract: A tape withdrawing member drive system forming a part of a loading mechanism for withdrawing a tape from a cassette for movement along a predetermined path of travel including gears driven from a motor through a rotation transmitting device, connecting linkages each including a plurality of joints supported at one end thereof by an end surface of one of the gears and engaging at the joint at the other end thereof one of tape withdrawing members.

Abstract: A tape transport mechanism for a recording and/or reproducing apparatus, such as, a cassette tape player, has supply and take-up reel shaft gears, a reverse gear mounted for axial movement parallel to the reel shafts between first and second positions in which the reverse gear meshes continuously with the supply reel shaft gear, a driving gear mounted for axial movement parallel to the reel shafts between first, second and third successively arranged positions, a rewind mode selecting device actuable to move the driving gear to its second position for meshing engagement with the reverse gear in its first position, whereby to drive the supply reel shaft through the reverse gear and the supply reel shaft gear, and a fast-forward mode selecting device actuable to move the driving gear to its third position while moving the reverse gear to the second position of the latter for disengaging the reverse gear from the driving gear and for engaging the driving gear with the take-up reel shaft gear.

Abstract: A floppy disk drive including a pivotally mounted disk pack storing a plurality of floppy diskettes, a driver mechanism for rotating any one of the diskettes into a retrievable position, a picker mechanism for moving the one diskette between the retrievable position and an operative position at which the diskette is rotatable on a spindle, and a position control circuit for controlling the position of a recording head across the one diskette being in the operative position and for compensating for expansion, contraction, and eccentric rotation of the one diskette. The floppy diskettes are stored bent in the disk pack, but in the operative position the one diskette that had been retrieved from the retrievable position is stored only partially in the disk pack and parallel to the plane of rotation. A microprocessor controls the entire disk drive.

Abstract: In a drive mechanism for a cassette tape recording/reproducing apparatus comprising a head base movable among the stop, pause and playback positions, a pair of capstans, and a pair of pinch rollers, a pair of assist gears adapted to be driven by the capstans and a pair of plungers are provided. When the first plunger is actuated to allow the first assist gear to rotate through its engagement with the forward capstan, selector means mounted on the head base is moved to the position engageable with the forward pinch roller and the head base is advanced to the pause position with the aid of the first assist gear. When the second plunger is further actuated, the head base is advanced to the playback position and the forward pinch roller is brought in contact with the forward pinch roller. The reverse operation can be done by actuating first the second plunger and then the first plunger.

Abstract: A cassette tape recorder comprises a multi-function eject lever rotatably mounted on a base board. The eject lever is provided with a guide pin for pushing a cassette toward the heads by engagement with an engagement hole of a cassette held in a cassette holder, and a pair of lock members engageable with the corresponding engagement members of the cassette holder to lock it in an inserted position when it is shifted from an eject position. A cam for rotating the erroneous erasure preventing lever by being pressed against the lateral side thereof is formed on the eject lever in the vicinity of one of the lock members.

Abstract: A carrying-arm arrangement for a magnetic disc store includes a movable carrying arm connected to at least one magnetic head. The magnetic head is shielded from spurious magnetic fields by a mu-metal shield which is connected to the arm and extends over the head.

Abstract: In a device for retrieving and recording (read/write) information on at least one rigid disk, a stepping motor servo system operated in an open-loop manner is provided to rapidly and accurately position read/write heads relative to the disk. A fixed guide shaft adjacent to and transverse to the motor shaft carries a carriage slidably thereon, preferably on oil impregnated bearings, the carriage member including a gear rack and the stepping motor having a pinion gear thereon interfacing with the gear rack. A preload bearing is urged against the carriage at a position between the guide shaft and the pinion gear such that the carriage is rotated around the guide shaft into engagement with the pinion gear at the rack portion thereof.