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:
Sep. 11, 1990
Filed:
Feb. 02, 1989
Applicant:
Inventors:
Clyde Robbins, Maple Glen, PA (US);
John Schilling, Dresher, PA (US);
Assignee:
General Instrument Corporation, New York, NY (US);
Attorney:
Primary Examiner:
Assistant Examiner:
Int. Cl.
CPC ...
H04N / ; H04N / ;
U.S. Cl.
CPC ...
380 19 ; 380-6 ; 358 86 ; 358143 ; 358144 ; 455-6 ;
Abstract
In order to provide secure access to the audio portion of a television signal, the audio portion of a TV signal is modulated at a frequency that is offset from the standard carrier frequency. In the embodiment disclosed herein, the audio portion of the TV signal is modulated with a nonstandard 4.75 Mhz carrier that is offset from the standard 4.5 Mhz carrier. In order that a standard TV receiver cannot receive the offset audio signal, the TV signal further contains an unmodulated carrier signal at 4.5 Mhz to 'blank' unauthorized reception.