HIGH SECURITY SUBSCRIPTION TELEVISION SYSTEM EMPLOYING REAL TIME CONTROL OF SUBSCRIBER'S PROGRAM RECEPTION

摘要

ABSTRACT OF THE DISCLOSUREA high security subscription television systemwhich includes the feature of dynamic scrambling anddescrambling of cable-connected television signals inresponse to real-time coded control signals. The systemalso has the ability to precisely tune the frequency con-verter unit at the subscriber's site, in response to realtime coded control signals provided by a computer at thecentral transmitting station. Various methods of scramblingand descrambling are described which use manipulation ofthe video signals at the baseband video level, and alsoat the RF level. Alternate embodiments of the descramblersinclude a secondary source for the reference carrier signalrequired for proper descrambler operation. In an ultra-stable embodiment of a subscriber's control terminal, asingle crystal controlled master oscillator is used tocontrol the frequency conversion unit, to provide a cleanreference carrier signal for the descrambler unit, and totune the control signal receiver, thereby removing the needfor frequent fine tuning control adjustments, and furtherallowing simplified system design and fabrication.