Picture carrier controlled automatic gain control circuit for cable television interdiction or jamming apparatus

Automatic gain control apparatus for automatically matching the power level of a broadband television signal transmitted toward a subscriber of an interdiction cable television system to a predetermined reference power level, the automatic gain control apparatus comprising:

• variable gain means for receiving the broadband television signal and adjusting the power level of the broadband television signal to match the predetermined reference level responsive to a control signal,
• filter means for passing a portion of the broadband television signal output of the variable gain means, the portion encompassing at least two adjacent television channels,
• level detector means for detecting the power level of the passed portion of the broadband television signal and providing an output signal representative thereof, and
• control means for comparing the output signal of the level detector means with the reference power level and providing the control signal to the variable gain means.

A method of automatically controlling gain of a broadband television signal for use in an interdiction CATV system comprising the steps of:

• a) measuring the power level of the broadband television signal at the output of variable gain means, wherein the power level measuring step comprises the steps of filtering the broadband television signal so as to pass at least two adjacent television channels and measuring the power level of the passed portion of the broadband television signal;
• b) comparing the measured power level with a predetermined reference power level, the reference power level being the sum of the signal attenuation between the variable gain means and a subscriber premises and a power level desired at the subscriber premises,
• c) determining the difference between the measured power level and the reference power level and
• d) adjusting the gain of the variable gain means in proportion to the determined difference;
• in a manner which attempts to null the difference.