Abstract: This invention discloses a new and improved method of scrambling video signals by inversion of the video information by splitting the sync pulse into plural portions and transmitting each portion of the sync pulse at a predetermined level. This improves the quality of the recovered video compared with other video inversion systems by rendering the video less sensitive to variations in the modulation depth of the modulator carrying the inverted signal, the demodulation sensitivity of the demodulator and the stability of the recovery circuits. The invention further provides additional security against pirating by allowing the scrambling circuit to operate in diverse modes, each of which will cause a TV to react differently should a conventional pirating device be employed. The invention also renders the signal capable of being transmitted with unmodified modulators of the type normally employed in the CATV industry.

Abstract: This invention discloses a new and improved method of scrambling video signals by inversion of the video information by splitting the sync pulse into plural portions and transmitting each portion of the sync pulse at a predetermined level. This improves the quality of the recovered video compared with other video inversion systems by rendering the video less sensitive to variations in the modulation depth of the modulator carrying the inverted signal, the demodulation sensitivity of the demodulator and the stability of the recovery circuits. The invention further provides additional security against pirating by allowing the scrambling circuit to operate in diverse modes, each of which will cause a TV to react differently should a conventional pirating device be employed. The invention also renders the signal capable of being transmitted with unmodified modulators of the type normally employed in the CATV industry.

Abstract: The present invention is directed to an inversion scrambler and unscrambler having pseudo-randomly controlled polarity-reversing switches to invert and re-invert, respectively, an audio signal so as to restrict the intelligent dissemination of the audio signal. To improve security of the scrambled signal, the audio signal is concealed prior to scrambling. Concealment includes clamping the original audio signal to a predetermined value and optionally offsetting this clamped signal prior to scrambling. The concealed signal is scrambled by inverting contiguous portions of the signal at pseudo-random intervals, accomplished by a polarity-reversing switching network controlled by a pseudo-random code generator. Upon unscrambling, artifacts will appear at the inversion points of the unscrambling signal, due to bandwidth limitations inherent in any transmission path.

Abstract: Scrambling and descrambling systems utilizing jamming signals provide improved pictures with minimal distortion due to ghosts and artifacts. The television signal is combined with a jamming signal or signals located preferably in the vestigial sideband (VSB) of the modulated picture carrier and at about a null in the spectrum of the modulation of the picture carrier by the horizontal sync. The jamming signal or signals also preferably are placed between the harmonic components of the horizontal sync which define the horizontal sync spectrum and at frequencies which comply with governmental regulations respecting frequency locations of strong signals of CATV purposes. The jamming signals are generated by phase locking to the horizontal sync signals of the television signals or to a submultiple of the horizontal sync frequency.

Abstract: A FM demodulator system which provides threshold extension by frequency selective phase modulation of the input FM signal in a band pass filter to reduce phase error between the input and output of the filter. The output of the filter is applied to an FM discriminator which provides a base band signal. This base band signal is applied to a frequency selective phase compensation network to derive a signal which phase modulates the band pass filter. The filter rejects uncorrelated thermal noise so as to effect threshold extension in the demodulator system.

Abstract: In an FM television signal angle modulated with luminance and chrominance information, there exists a high degree of correlation between picture elements occurring one line period apart. In an effort to steer the pass band of a tunable bandpass filter to the instantaneous frequency of the incoming television signal, a steering signal is developed which utilizes this high degree of correlation. For NTSC systems, luminance information is delayed by one-line period (63.5 .mu.s in the U.S.A.) and combined with suitably delayed chrominance information to form the filter's steering signal. For MAC systems, one-line delayed luminance and two-line delayed chrominance information are alternately applied to the filter as its steering signal. By steering the pass band of the filter to the incoming signal, maximum signal will be captured with minimum noise, enhancing the signal-to-noise ratio of a color television system.

Abstract: In an FM television signal angle modulated with luminance and chrominance information, there exists a high degree of correlation between picture elements occurring one line period apart. In an effort to steer the pass band of a tunable bandpass filter to the instantaneous frequency of the incoming television signal, a steering signal is developed which utilizes this high degree of correlation. For NTSC systems, luminance information is delayed by one-line period (63.5 us in the U.S.A.) and combined with suitable delayed chrominance information to form the filter's steering signal. For MAC systems, one-line delayed luminance and two-line delayed chrominance information are alternately applied to the filter as its steering signal. By steering the pass band of the filter to the incoming signal, maximum signal will be captured with minimum noise, enhancing the signal-to-noise ratio of a color television system.

Abstract: Suppressed sync TV signals are descrambled by restoring their sync intervals with restoring pulses generated in predetermined time relationship with timing pulses which are transmitted with the TV signals, amplitude modulated on the audio carrier (the center of the sound or audio frequency portion of the TV signal). The timing pulses are derived by intercarrier demodulation of the television signals which are transmitted on a RF (radio frequency) channel so as to avoid loss of the timing pulses in the event of deviation of the RF TV signals in frequency, either on transmission or due to frequency errors in an up/down converter which is tuned to select the RF TV channel.

Abstract: Subscription TV premium programming may be encoded with tagging information as by transmitting a tagging pulse during at least one horizontal line interval of each picture field in addition to pulses which are used to time the restoration of horizontal sync in the descrambler of a sync suppressed scrambling system. The additional tagging pulses provide information necessary to enable or disable the descrambler, and thereby provide high level encoding with minimum hardware complexity.

Abstract: Satellite tracking apparatus for use on board ship as part of a maritime communications satellite terminal is disclosed. A directional antenna which is adapted to be trained in the direction of the satellite so as to be in communication therewith is mounted so as to be positioned about three axes, namely train, elevation, and cross-level axes. The mount also has a fourth axis which is parallel to or collinear with one of the other axes. This fourth axis may be a level axis which is movable with the antenna. A stable platform is movable with and rotatable about the level axis. Sensors on this platform provide outputs to servo controllers which rotate the antenna about the elevation and cross-level axes to maintain the platform stable. An azimuth sensor such as a gyro compass and sensors responsive to angular motion with respect to the train axis may also be mounted on the platform and provide outputs to a servo controller which controls the bearing or azimuth position of the antenna.

Abstract: In an FM television signal angle modulated with luminance and chrominance information, there exists a high degree of correlation between picture elements occurring one line period apart. In an effort to steer the pass band of a tunable bandpass filter to the instantaneous frequency of the incoming television signal, a steering signal is developed which utilizes this high degree of correlation. For NTSC systems, luminance information is delayed by one-line period (63.5 us in the U.S.A.) and combined with suitable delayed chrominance information to form the filter's steering signal. For MAC systems, one-line delayed luminance and two-line delayed chrominance information are alternately applied to the filter as its steering signal. By steering the pass band of the filter to the incoming signal, maximum signal will be captured with minimum noise, enhancing the signal-to-noise ratio of a color television system.