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:
Oct. 14, 1986
Filed:
Aug. 26, 1983
Charles A Krause, Stevensville, MI (US);
Randy J Vander Heyden, Garland, TX (US);
Zenith Electronics Corporation, Glenview, IL (US);
Abstract
A multi-key keyboard is scanned at high speed in such a manner as to substantially reduce erroneous key entries caused by the simultaneous engagement of more than one key. A keyboard processor determines which key is down by sequential scanning of the keyboard, encodes the selected key and sends this code to a master processor, or CPU. A 2-key lockout scanning approach is employed wherein keyboard scanning stops when two keys are selected simultaneously. Scanning is resumed when either one or both of the first two keys are released. By limiting simultaneous key engagement detection to two keys, system complexity and cost are kept within reasonable limits while insuring against erroneous key entries. Detecting and storing the key engagement sequence permits a selected special function, e.g., automatic key repeat, to be applied to the last selected key rather than to an earlier selected, but simultaneously engaged, key.