The patent badge is an abbreviated version of the USPTO patent document. The patent badge does contain a link to the full patent document.
The patent badge is an abbreviated version of the USPTO patent document. The patent badge covers the following: Patent number, Date patent was issued, Date patent was filed, Title of the patent, Applicant, Inventor, Assignee, Attorney firm, Primary examiner, Assistant examiner, CPCs, and Abstract. The patent badge does contain a link to the full patent document (in Adobe Acrobat format, aka pdf). To download or print any patent click here.
Patent No.:
Date of Patent:
Aug. 28, 1990
Filed:
Jan. 23, 1989
Canon Kabushiki Kaisha, Tokyo, JP;
Abstract
An erasing device of the invention is adapted to erase information signals recorded in concentric circular tracks formed on a disc-shaped magnetic recording medium. A reference signal is first counted. According to the counted value, a plurality of kinds of first count data are caused to generate. Further, of the plurality of kinds of first count data, the first count data which represents a predetermined counted value is used to generate a reference erasing signal. Meanwhile, as the disc-shaped magnetic recording medium rotates, pulses are formed in synchronism with the period of its rotation. By counting the pulses, a second count data corresponding to the counted value is formed. To generate a first erasing pulse signal and a second erasing pulse signal in response to the reference erasing signal, the first count data and the second count data are compared with each other in magnitude. Depending on the result of that comparison, each of the pulse duties of the first and second erasing pulse signals is controlled. And, the thus controlled-in-pulse-duty first and second erasing pulse signals are added to form an erasing signal which is then supplied to the magnetic head, when the information signals recorded in the tracks on the disc-shaped magnetic recording medium are erased. By such construction and arrangement of the means, though in a very simple form, it becomes possible to erase the information signals recorded in the tracks on the disc-shaped magnetic recording medium with high reliability and in a short time.