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:
Apr. 30, 1985
Filed:
Aug. 23, 1982
Richard G Merrell, Hebron, IL (US);
Fredreck H Auld, Glenview, IL (US);
Zenith Electronics Corporation, Glenview, IL (US);
Abstract
A subscription television system includes a head-end for transmitting selected fields of a television signal in a scrambled form, the scrambled fields being identified by an encrypted mode control code inserted in a selected horizontal line of the preceding vertical interval. The mode control code is formed such that a predetermined non-transmitted control code is realized when the mode control code is processed with vertical interval system control data according to a selected function. A decoder processes the received mode control code and system control data according to the selected function to reconstitute the predetermined control code for enabling unscrambling of the following field. The decoder may employ majority voting techniques whereby not all of the bits of the reconstituted control code need be properly recovered to enable the unscrambling function.