Abstract: A system is disclosed for eliminating error in teletext signals caused by the presence of noise accompanying the teletext signals. The system includes: (1) a teletext packet buffer which receives the teletext signal and transfers the teletext signals to a teletext decoder in the absence of noise accompanying the teletext signals; (2) a timing circuit which produces timing signals from television synchronous signals; (3) a control circuit which controls the teletext packet buffer in response to the timing signals; and (4) a noise detector which detects whether noise is present in the teletext signal and disables the teletext packet buffer to prevent the transfer of the teletext signal from the teletext packet buffer to the teletext decoder if the teletext signal was received in the presence of noise.

Abstract: A television system having a fully compatible high-definition signal receivable at conventional resolution by conventional TV receivers without auxiliary apparatus with one TV channel carrying the conventional TV signal while high-frequency luminance and chrominance information is provided in a second TV channel. The high-frequency chrominance information is transmitted as two single sideband signals in the second TV channel. The baseband signal containing the high-frequency luminance components is derived from the lower sideband output of a product modulator whose inputs are taken from an anti-alias filtered camera which produces wideband luminance information and a local oscillator whose frequency is a multiple of the conventional chrominance subcarrier frequency embedded in the conventional baseband signal.

Abstract: A television system having a fully compatible high-definition signal with extended aspect ratio information receivable at conventional resolution by conventional TV receivers without auxiliary apparatus with one TV channel carrying the conventional TV signal while high-frequency luminance and chrominance information plus extended aspect ratio information are provided in a second TV channel. The extended aspect ratio information including luminance and chrominance information is transmitted during the horizontal retrace interval of the second TV channel. The extended aspect ratio chrominance information comprises I.sub.e and Q.sub.e segments which are transmitted during alternate horizontal retrace intervals. Since the segments are alternately transmitted, a storage mechanism is provided so that a segment received during a previous horizontal retrace interval can be reused during the present horizontal retrace interval for displaying the complete chrominance edge information.

Abstract: A low cost automatic equalizer is provided for reducing the amplitude and phase distortion produced by close-in echos. The color subcarrier burst, or some other portion of the video signal having predetermined amplitude and phase characteristic prior to transmission, is gated into detection circuitry. A regenerated color subcarrier, phase shifted to be in phase with the subcarrier burst, is used to detect the in-phase and quadrature components of the subcarrier burst, which are indicative of amplitude and phase distortion. The signals indicative of amplitude and phase distortion are applied to a three tap delay line equalizer, where the amplitude and polarity of the first and third tapped signals are controlled in unison to reduce amplitude distortion, and where the amplitude of the first and third tapped signals is controlled in unison, but the polarity of the first and third tapped signals is controlled oppositely to reduce phase distortion.

Abstract: A system for detecting phase distortion in video signals due to multipath effects includes circuitry for extracting the high and low frequency content of a horizontal synchronization signal, and for comparing the phase of the high frequency content to the low frequency content to produce a signal indicative of phase distortion in the video signal. The phase distortion signal may be applied to distortion reduction circuitry, and specifically in a three tap delay line equalizer, to reduce phase distortion in the video signal.

Abstract: A television tuning system employs a frequency synthesizer system for establishing the tuning of the receiver. A programmable frequency divider counter is connected between the output of a reference oscillator and a phase comparator to which the output of the local oscillator in the tuner also is applied. The phase comparator output provides a tuning voltage for controlling the tuning of the local oscillator. A microprocessor is used to control the count of the programmable frequency divider and initially to set a count corresponding to the selected channel in a counter connected between the output of the local oscillator and the phase comparator. The tuning consists of three discrete time periods. First, a settling time to allow channel change transients to settle; second, a short period of forced search at a relatively rapid rate to insure proper tuning; and third, a slower rate of step-by-step correction to accomodate for station drift and the like during reception.

Abstract: A digital to analog converter utilizes a digital missing pulse detector as a time interval measuring means in which the detector includes a programmable counter, the count of which is set to correspond with the digital number or word to be converted. Clock pulses at a high frequency are applied to advance the programmable counter from a reset condition to a terminal or output condition, and the time interval produced depends upon the binary word or number set into the programmable counter. Pulses at a second lower frequency, equal to the repetition rate of the system, are applied to the input of the time interval measuring circuit; so that the output is a series of pulse width modulated pulses having a duty cycle corresponding to the binary word originally set into the programmable counter.

Abstract: A television tuning system employs a frequency synthesizer system for establishing the tuning of the receiver. A programmable frequency divider counter is connected between the output of a reference oscillator and a phase comparator to which the output of the local oscillator in the tuner also is applied. The phase comparator output provides a tuning voltage for controlling the tuning of the local oscillator. A microprocessor is used to control the count of the programmable frequency divider and initially to set a count corresponding to the selected channel in a counter connected between the output of the local oscillator and the phase comparator. The AFT discriminator signal is used to sense the presence or absence of a properly tuned condition and to control the operation of the microprocessor for establishing the count in the programmable frequency divider counter.

Abstract: An automatic equalization circuit for a television receiver utilizes a portion of the VIR signal appearing in the conventional composite television signal as the training signal for the equalization circuit. A transversal filter in the form of a charge coupled device (CCD) clocked by a voltage controlled oscillator is used as the delay line for the equalization circuit. The output taps of the CCD are coupled through analog multipliers which, in turn, are provided with an error signal produced by the comparison between a reference signal and the output of an adder circuit connected to the outputs of all of the analog multipliers to vary the outputs of the analog multipliers in accordance with an error signal produced by the comparison circuit. The system also replaces the usual luminance delay line of a color television receiver, and the center tap of the CCD provides the delay normally imparted to the luminance signal components in such a receiver.

Abstract: Auxiliary signals suitable for conveying additional audio signals for stereophonic television broadcasts, bilingual sound, and the like, are transmitted in the form of modulated bursts of such auxiliary signal placed on the front porch of the composite video signal and continued through the vertical synchronization pulse intervals. At the receiver, a transmission gate is connected to receive the composite video signal and has an output coupled to an auxiliary signal demodulation circuit. The transmission gate is operated to pass only the auxiliary signal bursts in response to control signals obtained from the sweep circuit of the television receiver. By utilizing composite AM/FM modulation of the auxiliary signal or by employing quadrature modulation, dual or stereophonic sound signals may be obtained for reproduction with corresponding output utilization circuitry.

Abstract: A system is used in conjunction with a color television receiver for forcing rapid chroma transients to be applied to the color picture tube in response to the sensing of transients in the chroma signal by establishing a predicted new signal level and applying such new signal level as an overriding signal to the input to the color picture tube for a predetermined time interval following the beginning of a sensed chroma transient.

Abstract: A phase locked loop system having improved acquisition time is particularly suitable for use in a television receiver with frequency synthesizer tuning. A conventional phase locked loop is modified by the addition of a pair of transmission gates and a frequency discriminator/detector. The transmission gates are normally open, and the phase locked loop system operates in a conventional manner. When a programmable frequency divider connected between the output of the voltage controlled oscillator and the input to the phase locked loop phase comparator has its division ratio changed to select a new channel, the frequency discriminator, which also is connected to the output of the programmable frequency divider, applies an appropriate gating signal to one or the other of the transmission gates to close that gate.

Abstract: An improved vertical synchronization system for a television receiver provides both good noise immunity and improved interlace. This is achieved by employing two parallel vertical synchronization circuits between the synchronizing signal input of the vertical oscillator and synchronizing signal source. One of these vertical synchronizing circuit paths comprises a standard integrator circuit adjusted for optimum noise immunity and the other is a cascaded digital circuit adjusted for improved interlace but having poorer noise immunity than the first circuit. The digital circuit produces a synchronizing pulse slightly ahead of the pulse produced by the conventional circuit so that the digital circuit normally controls the operation of the oscillator. Whenever extreme noise conditions exist, the digital circuit is disabled and the conventional synchronizing signal circuit takes over the synchronizing task.

Abstract: A television tuning system employs a frequency synthesizer system for establishing the tuning of the receiver. A first programmable frequency divider controlled by a reversible counter is connected between the output of a reference oscillator and a phase comparator to which the output of the local oscillator, after passing through another programmable frequency divider, also is applied. The phase comparator output is a tuning voltage used to control the tuning of the local oscillator. A logic circuit responsive to characteristics of the received signals changes the count in the reversible binary counter to adjust the first programmable frequency divider to compensate for channel frequency offsets which may occur in excess of the pull-in range of the AFT discriminator circuit. To permit operation of the receiver as a signal seek receiver, a pair of signal seek push buttons for the "up" and for the "down" direction, respectively, are provided.

Abstract: A frequency selective detector circuit is useful as a high/low pass detector or as a bandpass detector. The high/low pass detector comprises a pair of digital missing pulse detector circuits or resettable one-shot multivibrators that are connected together in cascade between a source of input pulses and the detector circuit output. The timing interval of the first missing pulse detector circuit in the cascade is less than the timing interval of the second missing pulse detector circuit in the cascade. By combining two such circuits to supply their outputs to a coincidence gate, a bandpass detector circuit results.

Abstract: A low level video auxiliary signal is transmitted in addition to the conventional composite black and white or color television signal. The auxiliary signal is in the form of redundant, opposite-polarity signal portions during pairs of time successive signal portions, such as horizontal lines or fields of the composite television signal. The auxiliary signal also may be transmitted in the form of a predetermined frequency with the auxiliary information on successive lines of the composite television signal being out of phase by one-half the period of the auxiliary signal frequency. When the composite signal is detected and displayed by the conventional circuitry in the receiver, the auxiliary information is visually cancelled in the image displayed on the cathode ray tube and the normal video information is displayed.

Abstract: An automatic hue control system operates to correct the phase of the color subcarrier reference signal used to operate the demodulators of a color television receiver. A regenerated color subcarrier signal at the phase of the I axis or the axis of flesh color is fed to one input of a phase comparator. The amplitude limited chrominance signal is fed to another input of the phase comparator, the output of which is used to operate a single pole double throw switch circuit. The switch passes the regenerated subcarrier signal to the demodulators when the phase difference between the limited chrominance and the regenerated subcarrier signals is outside a predetermined angle on each side of the I or flesh axis.

Abstract: A television receiver includes a provision for processing auxiliary signals in addition to the conventional information signals. The auxiliary signals comprise various combinations of N signals out of a total of M possible signals, where N and M are positive integers greater than 1, and N is less than M. The auxiliary signals preferably are audio signals outside the normal audible range, and the decoding of unique combinations of these signals at a receiver is used to provide channel number identification when the signals are transmitted from transmitting stations. In addition, the auxiliary signals transmitted from a transmitting station are used to control signal-seek tuning, direct channel access, or channel display. Also, unique combinations of N out of M possible signals are used in a remote control system to provide output signals indicative of different functions to be performed by the television receiver.

Abstract: A television tuning system employs a frequency synthesizer system for establishing the tuning of the receiver. A first programmable frequency divider controlled by a reversible counter is connected between the output of a reference oscillator and a phase comparator to which the output of the local oscillator, after passing through another programmable frequency divider, also is applied. The phase comparator output is a tuning voltage used to control the tuning of the local oscillator. A logic circuit is coupled to sense predetermined relationships of signals from a picture carrier detector, a sound carrier detector, an AFT discriminator circuit, and the presence of vertical synchronization signal components for changing the count in the reversible binary counter to adjust the first programmable frequency divider to compensate for channel frequency offsets which may occur in excess of the pull-in range of the AFT discriminator circuit.

Abstract: A television tuning system employs a frequency synthesizer system for establishing the tuning of the receiver. A first programmable frequency divider controlled by a reversible counter is connected between the output of a reference oscillator and a phase comparator to which the output of the local oscillator, after passing through another programmable frequency divider, also is applied. The phase comparator output is a tuning voltage used to control the tuning of the local oscillator. A logic circuit is coupled to sense predetermined relationships of signals from a picture carrier detector, a sound carrier detector, an AFT signal, and the presence of vertical synchronization signal components for changing the count in the reversible binary counter to adjust the first programmable frequency divider to compensate for channel frequency offsets which may occur in excess of the pull-in range of the AFT circuit.