| 摘要 |
An off-premises i.e. a negative or positive trap, jamming cable television or interdiction system, includes a picture carried controlled automatic gain control circuit. A broadband television signal output of a variable gain device is distributed by a radio frequency signal splitter to a number of subscribers. A portion of the output of the variable gain device comprising at least two contiguous television channels is passed to a power level detector. A detected power level is compared with a predetermined power level reference for adjusting the gain of the variable gain device. The predetermined power level reference is set to equal the attenuation between the off-premises equipment and the subscriber premises plus the desired level at the entrance to the subscriber's premises. The power level of a jamming or interdicting 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. |
