Abstract: Utilizing the technique whereby particulate media electrodeposited at a critical electric field intensity has a given packing density, and when electrodeposited at a lesser electric field intensity has a lower density, the present invention teaches electrodeposition of media whose particulate packing density varies in accordance with an areally predetermined pattern. The pattern is incised in one electrode of the deposition apparatus, and the medium as deposited on the other electrode mirrors the pattern as a varying particulate packing density. The packing density varies with the electric field intensity, and the electric field varies due to the unequal interelectrode distances arising from the incisions in the electrode. The medium is then magnetized, and the density variation provides a d.c. magnetically reproducible signal in accordance with the pattern.

Abstract: A particularized cross section for a magnetic recording head provides a constant area wear profile for cooperating magnetic tape. The constant area wear profile results from the "combined" use of a common radius of curvature for both the natural bending radius of the tape as well as the tape-contacting surface of the head, taken together with the requirement that the leading and trailing medium-contacting parts of the head form air-skiving edges which are essentially parallel to the force- (or pressure-) direction associated with the tape-contacting interface.

Abstract: In a magnetoresistive reproduce head which is self-biased by a saturated soft adjacent layer magnetically coupled to the magnetoresistive element, the induced anisotropy fields of the magnetoresistive element and the soft adjacent layer are made to lie in the direction of the bias field at the magnetoresistive element rather than perpendicular to the bias field. These induced anistropy fields partially counteract demagnetizing fields which oppose the bias field, and thereby lower the current in the magnetoresistive element required to saturate the soft adjacent layer in biasing the magnetoresistive element. The lowered current reduces the Joule heating of the magnetoresistive element and attendantly results in improved head performance.

Abstract: Utilizing the technique whereby particulate media electrodeposited at a critical electric field intensity has a given packing density, and when electrodeposited at a lesser electric field intensity has a lower density, the present invention teaches electrodeposition of media whose particulate packing density varies in accordance with an areally predetermined pattern. The pattern is incised in one electrode of the deposition apparatus, and the medium as deposited on the other electrode mirrors the pattern as a varying particulate packing density. The packing density varies with the electric field intensity, and the electric field varies due to the unequal interelectrode distances arising from the incisions in the electrode. The medium is then d.c. magnetized, and the density variation provides a magnetically reproducible signal in accordance with the pattern.

Abstract: A ferrimagnetic medium is locally heated above its compensation temperature and a magnetic record head provides a magnetic field for data recording on the heated portion of the medium. Upon re-cooling to the compensation temperature, the recorded signal is magnetically "locked" in the medium. The user of a magnetic head to provide the recording magnetic field allows fast head current switching rates with attendant high density data recording or high speed erasure of the medium. The recorded medium is read by means of conventional magneto-optic apparatus.

Abstract: A self-biased magnetoresistive reproduce head is excited with an a.c. sense current which simultaneously a.c. biases the magnetoresistive element. When reproducing a pre-recorded signal, the spectrum of the head output includes sidebands containing the signal information associated with a suppressed carrier at twice the bias frequency. These sidebands are far removed in the head output frequency spectrum from sources of low frequency noise. The invention teaches demodulating these sidebands by means of a locally generated carrier corresponding to the suppressed carrier which has a frequency of twice the bias frequency. This locally generated carrier is coherent with the bias frequency source. The information signal is thereby recovered in a portion of the spectrum immune from the effects of low frequency interfering noise.

Abstract: Correction of PCM digital image data by encoding of the redundancy present in blocks of the data may be subject to faulty encoding for certain amounts of redundancy. This occurs at the boundaries where the data values change from 255-256, 127-128 and 63-64, because all the binary bits of the representation change at these values. The improved apparatus of the invention encodes the redundancy in blocks of data by assignment of check bits in terms of the data magnitudes, and does not rely on the PCM binary representation to express the redundancy. Upon decoding, the recovered data redundancy is compared to the redundancy represented by the received check bits, and its magnitude is used to determine the data in error. The value in error is replaced by the average of the data values in the same block.

Abstract: A magnetic recording medium is fabricated by the electrodeposition of acicular magnetic particles onto an electrically conductive substrate from a mixture that is continuously dispersed and circulated through the electrodeposition vessel. Electrodeposition is effected at a critical electric field strength so that the particles are aligned in solution, and deposited perpendicular to the substrate surface such that the medium is highly densified. By use of anisotropic particles the resultant medium is adaptable for perpendicular recording, and by use of isotropic particles the resultant medium will support both longitudinal and perpendicular recording.

Abstract: The sample values of a digitized image are encoded utilizing the amount of redundancy in the digital data to generate check bits which are attached to blocks of the data prior to transmission or recording. After transmission or recording, the recovered data is re-encoded using the original encoding rules, and any resultant errors which have changed the redundancy are reflected in the re-encoded check bits. The original check bits attached to the data are compared to the re-encoded check bits to determine if the errors are correctable, and, if so, what steps must be taken to correct the errors and to restore the original redundancy to the recovered data. Two implementations for the practice of the invention are presented.

Abstract: A plastic cassette, having reel hub spindles and tape guides which are accurately machined inserts, is used as a tape supply and take-up container for a reel periphery driven tape transport. The reel hub spindle and the tape guide bases are accurately machined reference surfaces, and the spindles and guides are flexibly captive in the cassette shell with their reference surfaces extending below the cassette shell. Upon insertion into the transport, the reel hub spindle and tape guide bases are forced into abutment with a reference surface of the transport, causing the cassette tape path to conform to the transport tape path, substantially independent of the orientation of the plastic cassette body relative to the transport.

Abstract: In equalizing a digital channel, impulses are applied to the channel input at the Nyquist rate. The channel response is sampled to determine its amplitude values of specified sampling times, and the amplitude values are converted into corresponding pulse duration signals. The pulse duration signals are applied to a time interval analyzer whereby the signal input durations are displayed in the form of a histogram showing the number of pulses of a given duration as a function of pulse duration. The time dispersion of the displayed pulse durations measures the intersymbol interference present, and is a measure of the quality of the equalization.

Abstract: A planar array of high track density magnetic heads is mounted on a piezoelectric structural member. The heads are in contact with an area of magnetic recording medium coated onto a stationary support member located adjacent the head array structure. A repetitive ramp voltage is applied to the piezoelectric member causing repetitive linear extension of the member with resultant relative motion between the head array and the medium. A position transducer provides a feedback signal which monitors the position of the head array in relation to the magnetic medium, and this feedback signal is used to servo control the motion of the head array. Recording and playback of the stored information occurs coincidentally with the movement of the head array relative to the medium.