Cryptography – Cryptanalysis
Patent
1990-11-28
1994-09-06
Gregory, Bernarr E.
Cryptography
Cryptanalysis
348 6, 455 31, 4552331, 4552341, 4552391, 4552401, 4552461, H04N 7167
Patent
active
053455045
ABSTRACT:
A off-premises CATV system includes a compensation control including a picture carrier controlled automatic gain control and an automatic slope control. A broadband television signal output from a variable gain device is distributed by a radio frequency signal splitter to a number of subscribers interdiction. The variable gain device and a variable frequency dependent device are connected in series for automatic gain control and automatic slope control, respectively. A first feedback control is used to compare a first portion of the broadband television signal to a reference power level and null the error. A second feedback control is used to compare a second portion of the broadband signal to the first portion and null the error. A second embodiment of the second feedback control differences the first and second portions of the broadband television signal. The first predetermined portion is a band of frequencies (high band) between 250 MHz. and 310 MHz. and the second predetermined portion is a band of frequencies (low band) between 54 MHz. and 150 MHz. The predetermined power level reference for automatic gain control is set to equal the attenuation between the off-premises equipment and the subscriber premises plus the desired level at the subscriber premises. The power level of a jamming signal for denying access to unauthorized television programs is set to fall within a predetermined range of power levels related to the predetermined power level reference.
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Gregory Bernarr E.
Scientific-Atlanta, Inc.
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