Abstract: Apparatus, for recording information on a flexible magnetic slave disk by contact transfer of information recorded on a flexible magnetic master disk, includes a U-shaped electromagnetic device terminating, respectively, in a first planar pole tip axially aligned with a second movably mounted planar pole tip, to define predominately a single closed-loop flux-conducting path extending through a contact-transfer zone between the pole tips. A linear actuator, coupled to the movable pole tip, serves for releasably mounting the master disk in intimate facing relationship with the slave disk in the contact-transfer zone between the planar pole tips. Control circuitry applies an alternating electrical signal to the U-shaped electromagnetic device to develop an alternating magnetic field in the closed-loop flux-contacting path that produces a corresponding alternating magnetic transfer field extending axially in the contact-transfer zone between the planar pole tips.

Abstract: Electromagnetic drive circuitry, for recording information on a flexible magnetic slave disk by contact transfer of information recorded on a flexible magnetic master disk, includes a U-shaped electromagnetic device terminating, respectively, in a first planar pole tip axially aligned with a second movably mounted planar pole tip, to define a closed-loop flux-conducting path extending through a contact-transfer zone between the pole tips. The drive circuitry further includes signal-modulating circuitry for applying an alternating voltage of progressively decreasing amplitude to the electromagnetic device, to develop an alternating magnetic field of progressively diminishing strength in the closed-loop flux-conducting path that produces a corresponding alternating magnetic transfer field extending axially in the contact-transfer zone between the planar pole tips.

Abstract: A method for modulating binary data into a format suitable for encoding and decoding information, that employs a non-return-to-zero (NRZ) technique. The modulating method includes: defining within a recording medium an event-cell as the time between two adjacent clock transitions having a similar, unique characteristic; and, selectively writing to the recording medium within the event-cell, at an arbitrary time, either a first or a second information. The selective writing step includes generating a first event and a corresponding first read signal in response to a first information and generating a second event and a corresponding second read signal in response to the second information. The method can be employed for a first situation where the information transfer rate during the modulating process is well-regulated, and is advantageously employed for a second situation where the information transfer rate is dependent on unpredictable and variable transfer rate velocities and accelerations.

Abstract: Trackwise disparity between inductive record and magneto-resistive playback heads which are built on a common support is measured and memorized. Thereafter, during head-positioning, the memorized disparity is employed as a track-address bias for proper registration of the playback head, irrespective of its widthwise disparity relative to the record head. To achieve the aforesaid measurement, the invention provides for a self-calibrating algorithmic routine that generates the aforesaid bias.

Abstract: A quaternary saturated digital magnetic recording system for enhancing information entropy provides an effective bit density increase of 100% or more over the MFM code. In the simplest implementation, groups of two input binary bits are mapped into one data cell, preferably into four combinations of long or short breaks and positive or negative polarity, with the break optionally centralized within the data cell for self-clocking. A system for reproducing the recorded information provides a peak detector, responsive to the recorded signal, coupled to pulse polarity and break width detector circuitry, with an internally synchronized clock, for remapping the recorded data into binary format.

Abstract: An automatically adjustable equalizer for modifying the spectral contour of digital, analog, and magnetically recorded signals. A temperature sensor-controlled switching circuit automatically adjusts the delay and forward gain parameters of the equalizer so as to optimize the equalization contour, in discrete ranges, over a wide range of temperatures, pressures or other physical processes or conditions.

Abstract: The Controlled Return to A.C. (CRA) magnetic recording and reproducing system applies a high frequency erase signal continuously to the write head except at the detents. At the detents polarity controlled interruptions of the high frequency erase signal are embedded therein. A positive interruption, a negative interruption and the absence of an interruption provides a ternary recording capability at the detent. The high frequency erase signal is controlled in phase to provide polarity coherent interruptions. A CRA cell includes two controlled interruptions providing a mapping of three binary digits into two CRA digits. The controlled interruption results in an opposite polarity pulse pair upon readback.

Abstract: A thin film magnetic read/write transducer has a substrate of magnetic material forming a pair of disparate pole pieces. Arranged adjacent a movable magnetic medium, the disparate pole pieces are constructed so that the leading pole piece has a greater distal surface area than the trailing pole piece. In an alternative arrangement the leading pole piece distal surface is disposed a greater distance from the medium than the trailing pole piece. In yet another arrangement the trailing pole piece distal surface is disposed at an acute angle to the medium, and the leading pole piece surface may be at a lesser angle or parallel to the medium. The disparate pole pieces, so constructed and arranged, introduce compensating non-linearities to the writing magnetic field to substantially counteract the non-linear properties of the medium and of the recording process.

Abstract: A detector for determining whether the time duration between a positive and a negative peak of a waveform is greater or less than a predetermined time interval comprises a delay line for delaying the waveform by the predetermined time interval. A peak detector of a first polarity for detecting the first occurring peak of the waveform is responsive to the delayed waveform to provide a signal upon the occurrence of the first occurring peak thereof. A peak detector of a second polarity for detecting the second occurring peak of the waveform is responsive to the undelayed waveform for providing a signal upon the occurrence of the second occurring peak thereof. A time sequence comparator provides a first output indication when the signal from the first peak detector occurs prior to the signal from the second peak detector and a second output indication when the signal from the second peak detector occurs prior to the signal from the first peak detector.

Abstract: The transducer for perpendicular magnetic recording comprises a core of high permeability material having a recording pole and a flux return pole spaced apart and connected by an intermediate member forming an inverted generally U-shaped core. The cross sectional area of the flux return pole is substantially greater than that of the recording pole. Current applied to a coil wound around the recording pole generates flux for recording on the magnetic medium. A similarly shaped second core may be disposed on the opposite side of the medium with respect to the first core for providing a flux return path for the first core. A sub-core of high permeability material mounted on the flux return pole forms a gap with the recording pole to provide a ring-type head for data recovery. Current applied to a coil wound on the sub-core saturates the sub-core to render it ineffective during perpendicular magnetic writing.

Abstract: In a feedback control system wherein data pulses also establish timing coordination between the data and the processing devices, two delay circuits are provided to extract the synchronized clock pulses from the coded incoming signal. This enables relative digital decoding and ensures a precise data transfer to a computer interface. One of the delay circuits enables a data reconditioner circuit to buffer the data and eliminates data peak shifting. The reconditioned data is provided to a coincident circuit which selectively transfers the data to a computer interface and to a phase difference detector. The other delay circuit provides to the phase difference detector a second input corresponding in time to the coded incoming data pulses. The detector's output generates a DC error voltage which synchronizes a voltage controlled oscillator (VCO). The outputs of the VCO are clock pulses in phase with the coded incoming signals.

Abstract: A zero-crossing detecting circuit where the input signal is applied to positive and negative threshold circuits. Each threshold circuit is connected to the input of a respective one-shot circuit which responds to the beginning edge of each output signal from its threshold circuit. The output pulses of both one-shots are applied to a NOR circuit which thereby responds to the beginning edges but not the trailing edges of the signals from the threshold circuits. Accordingly, variations in the trailing edges of the signals from the threshold circuits due to hysteresis or varying propogation times do not effect the circuit's output.