International Business Machines Corporation

Jeffrey L Lovgren

Daniel O Castrodale

Karl A Shidler

John T Trnka

George C Thomas

Richard B Bhend

William B Plummer

William P Quinlan

Georg Gaebelein, Deceased

John R Mercer

Ralph A Russell

Robert D Keillor

A variable time integrating period to accomplish distortion free synchronization of the scanning rate to the document transport speed when the transport speed is within a predetermined tolerance with respect to it's nominal speed is disclosed. The rate levels provided by the scanner are then multiplied by an appropriate correction factor to compensate for the varied amount of light accumulated by the time integrating photo sensor array because of the varied integration time. When the document speed must be reduced to a value less than the predetermined tolerance, the system of the invention resorts to the techinque of selecting only certain scans and discarding the data from other scans. Scan selection is found to be economically accomplished by selecting those scans which were time integrating when an emitter pulse occurred.

Solid state scanner for a variable speed transport

A diskette identifying code is written in each sector on a flexible disk used in a flexible disk recorder. The diskette identifying code can be read from any track on the flexible disk and used to log the occurrence of insertion or removal of the diskette at the flexible disk recorder. Also, the diskette identifying code can be read from any accessed track prior to a write operation on that track in order to verify that the diskette has not been changed by the operator since the last access to the flexible disk.

Method for checking disk identity in a flexible disk recorder

The digital-to-analog converter described herein generates an analog signal level from a digital value and a modulation coefficient. The converter modulates the digital word applied to the conversion stages and smoothes the resultant duty cycle modulated analog levels to produce additional analog levels between the normal levels provided by the conversion stages of the DAC. In one embodiment the duty cycle modulation of the digital value is accomplished by a rate multiplier controlling the incrementing of the digital word applied to the conversion stages. In another embodiment of the invention, the duty cycle modulation of the digital word is performed by a microcomputer. A low pass filter or a DC motor is used to smooth or filter the duty cycle modulated levels from the conversion stages.

Digital-to-analog converter

A control system for applying a magnetic head onto a magnetic disk in random places thereon including a free running oscillator and switching means responsive to pulses from said oscillator and a head load command signal derived from the disk during a revolution thereof for initiating the energization of a head engaging solenoid. The system includes a capacitor which is charged at various rates to produce an initial fast rising current in the solenoid for moving the head into close proximity with the disk, a slowly rising subsequent current in the solenoid for engaging the head with the disk gradually, and a final fast rising current in the solenoid for completing the engagement of the head on the disk.

Magnetic head load control system

A magnetic head or transducer assembly for cooperating with a relatively moving magnetic medium and for reading and/or writing a track of magnetic information on the medium and for erasing the edges of the track and old information adjacent to the edges of a newly written track. The head comprises a central magnetic core with a gap on an active face of the head assembly and with a read/write coil on the magnetic core and comprises a pair of additional, erase magnetic cores on opposite sides of the central magnetic core and forming a pair of erase gaps on the active face of the head assembly. A single erase coil is disposed on opposite legs of the erase cores, and an L-shaped side bar completes the erase magnetic circuit for both of the erase cores and lies on one end of the erase coil and provides an air gap between it and the ends of each of these erase core legs so as to cause the action of the two erase gaps to be equal in their erasing action.

Growing community of inventors

Rochester, MN, United States of America

Jeffrey L Lovgren