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:
Feb. 13, 2001
Filed:
Oct. 07, 1996
Joseph Glaab, New Hope, PA (US);
General Instrument Corporation, Horsham, PA (US);
Abstract
The passive interdiction system for CATV scrambling provides a plurality of passive, preselected negative signal traps for securing specific CATV channels. Each trap cyclically attenuates the desired CATV channel thereby confusing the AGC (automatic gain control) circuit of the television monitor-receiver or video cassette recorder (VCR) by rapid cancellation and restoration of the picture carrier and main signal components. The passive interdiction system is comprised of a plurality of SAW (surface acoustic wave) resonators tuned to specific frequencies corresponding to the carrier frequencies of the channels to be secured and are alternately keyed on and off by a 10 to 20 Hz square wave. Authorization and control of the secured channels originates at the cable provider's headend and is transmitted contemporaneously with the CATV programming. The authorization data is specifically addressed and decoded at unique interdiction units disposed within the CATV system. The SAW resonators exhibit a low value temperature coefficient yielding stable trap frequency responses.