초록 ▼

An off-premises cable television interdiction apparatus provides a microprocessor controller for controlling and switching one or more variable frequency voltage controlled oscillators. The variable frequency oscillators selectively jam only unauthorized premium programming transmitted on particular

An off-premises cable television interdiction apparatus provides a microprocessor controller for controlling and switching one or more variable frequency voltage controlled oscillators. The variable frequency oscillators selectively jam only unauthorized premium programming transmitted on particular channels of a broadband signal in the clear from a headend to a subscriber. The microprocessor controller controls the variable frequency oscillators to hop between jamming frequencies and jam particular channels under control from the headend. A frequency calibration routine is executed periodically upon power-up to determine gain parameters for the oscillators. A heterodyned variable frequency oscillator may be provided for the interdiction system which moves the frequency of the variable frequency oscillator out of the television band and mixes the variable frequency oscillator output with a fixed local oscillator output to provide a jamming signal that falls in the television band. Gain control using a heterodyned oscillator may instead be provided for use in the interdiction system which uses one channel of the broadband signal as the jamming signal. Automatic gain control may also instead be provided for controlling the attenuation of a variable attenuator in accordance with a gain function determined by interpolation and previously stored in memory by a calibration routine executed periodically or upon power-up. The calibration routine may run concurrently with a frequency calibration routine for controlling the frequency of the jamming signal.

대표청구항 ▼

Gain control apparatus for use in a television premium channel interdiction system for selectively jamming unauthorized premium programs on a broadband signal transmitted to a subscriber, comprising: jamming oscillator means for generating a jamming signal; variable attenuator means for attenuating

Gain control apparatus for use in a television premium channel interdiction system for selectively jamming unauthorized premium programs on a broadband signal transmitted to a subscriber, comprising: jamming oscillator means for generating a jamming signal; variable attenuator means for attenuating the jamming signal in accordance with a control signal to produce an attenuated jamming signal; combiner means for combining the attenuated jamming signal with the broadband signal to produce a jammed signal; first comparator means for comparing a magnitude of the attenuated jamming signal with the broadband signal; and controller means for determining and providing the control signal to said variable attenuator means in accordance with a predetermined function of a frequency of said jamming oscillator.