Abstract: An analog front end. The analog front end comprises a converter configured to convert a differential input signal to a single-ended input signal, and convert a single-ended output signal to a differential output signal. And a transformer configured to couple the differential input signal from a twisted pair telephone line to the converter, and couple the differential output signal from the converter to the twisted pair telephone line.

Abstract: An integrated communications system. A substrate having a receiver disposed on the substrate for converting a received signal to an IF signal, a digital IF demodulator disposed on the substrate and coupled to the receiver for converting the IF signal to a demodulated baseband signal, and a transmitter disposed on the substrate operating in cooperation with the receiver to establish a two way communications path.

Abstract: An analog front end. The analog front end comprises a converter configured to convert a differential input signal to a single-ended input signal, and convert a single-ended output signal to a differential output signal. And a transformer configured to couple the differential input signal from a twisted pair telephone line to the converter, and couple the differential output signal from the converter to the twisted pair telephone line.

Abstract: A plurality of video lines in a raster scan video image are scrambled by delaying a first video line in time equal to the horizontal line scan time for the raster scan video field to produce a delayed first video line. The delayed first video line is inverted to produce an inverted delayed first video line and one of the delayed first video line, the inverted delayed first video line and a null signal is added to a second horizontal video line to produce a horizontal line of a scrambled video signal. The scrambled horizontal lines of video information are descrambled by delaying a first scrambled horizontal video line in time equal to the horizontal line scan time for the raster scan video field to produce a delayed first scrambled video line.

Abstract: The converter has two mixer stages each including a phase locked loop with an oscillator controlled by a phase comparator. The frequency reference to both stages is provided by a single master reference. The frequency of the oscillator in the first stage is offset to accommodate the three different broadcast frequency conventions. A high frequency reference permits the second stage to compensate for noise kilohertz away from the carrier. A local oscillator output which is also phase locked to the master reference is provided for an external video modulator.

Abstract: An on channel frequency agile PLL demodulator is provided using a precise and stable oscillator, such as a VCXO having its output frequency variable over a limited range. The output of the oscillator is multiplied by a multiplication factor to produce a mixing frequency. The multiplication factor scales the limited range of the oscillator to produce a proportionate mixing frequency deviation. A frequency synthesizer is used to enable the demodulator to detect signals on different channels. In one embodiment, the output of the frequency synthesizer is mixed with the scaled oscillator output to provide a mixing frequency having a fixed deviation for all channels.

Abstract: A carrier is received containing a plurality of signals within a first frequency band, for example television signals within the cable television band. The signals are upconverted to a second frequency band above the first band wherein a selected one of the upconverted signals will reside at an intermediate frequency within the second band. The selected upconverted signal is input to a homodyne detector operating at or near intermediate frequency. In-phase and quadrature signals output from the homodyne detector are digitally processed to recover a baseband signal.

Abstract: A method and apparatus are provided for descrambling a sinewave scrambled television signal. The television signal is applied to a dual loop circuit that detects AM sinewave modulation on the television signal sound carrier. The detected modulation is applied to the picture carrier of the television signal in a first loop of the circuit to cancel the AM sinewave modulation therefrom. The detected modulation is applied to the sound carrier of the television signal in a second loop of the circuit to increase the AM sinewave modulation on the sound carrier within the loop. The net loop gain of the first loop is then lowered to minimize the application of noise from the sound carrier to the picture carrier.

Abstract: Circuitry for producing an extremely linear frequency modulated audio carrier for use in the head end of a video signal distribution system, such as a cable television system. A reference oscillator operating at a relatively high frequency, such as the video carrier frequency, generates a signal which is divided down to a relatively low frequency. A voltage controlled oscillator operating at the relatively low frequency is used to frequency modulate the audio signal. After modulation, the audio carrier is upconverted utilizing a signal frequency which is also derived from the original reference frequency, thus providing a stable and linear frequency modulated audio carrier particularly suitable for transmission of stereo program audio.