Abstract:
A set-top teletext converter decodes the chroma burst signal of a color television signal with the substantially same amplitude and phase as the burst in the television signal. The teletext signal along with its transparent mode signal are decoded. The decoded teletext signal is then re-encoded as a standard television signal using the decoded burst signal. When switching between the encoded teletext signal and the regular television signal under the control of the transparent mode signal, no color shift is present.
Abstract:
Changes in the support forces on a structural member when it is touched are used to compute the location of the point at which the structural member is touched.
Abstract:
A video disc playback system having digital circuitry for detecting degradation in recovered signal. Circuitry is included to determine probable errors in the digital components of signal recovered from the disc record. A digital reference number is generated by storing a valid digital number recovered from the disc and incrementing that number by a constant in accordance with the normal progression of numbers prerecorded on the disc. The recovered numbers are compared with the generated reference numbers to generate an error signal on mismatch. The error signal is used to weight a constant binary number by one or zero, the result being added to an accumulated error function. The sum is weighted, the result becoming the updated accumulated error function for the next iteration on the occurrence of the subsequently recovered digital number. The weighted sum is also compared against a predetermined value and a control signal is generated on the weighted sum exceeding the predetermined value. The control signal is used to attempt to overcome at least one cause of the signal degradation.
Abstract:
A tuning system of a television receiver includes a memory with a plurality of memory locations for storing tuning information associated with various channels a viewer may select. Each memory location includes a display portion for storing a binary word representing, in BCD format, information for displaying the channel number of an associated channel and a tuning voltage portion for storing a binary word representing information for generating the appropriate tuning voltage for the associated channel. When it is desired to have a channel skipped over during the normal channel selection mode of operation of the tuning system, in response to viewer control, an input complementor complements each of the binary signals of the binary word stored in the display portion of the associated memory location to form the "1s" complement of the binary word representing the channel number of the channel and thereby identify the associated channel as a nonpreferred channel. Since the "1s" complements of the binary words representing channel numbers between 2 and 83 represent illegal channel numbers, (i.e., channel numbers not between 2 and 83), an illegal channel number decoder is used to cause memory locations containing binary signals representing illegal channel number to be skipped during the normal channel selection mode of operation of the tuning system. When it is desired to reinstate a previously skipped channel, an output complementor, in response to viewer control, recomplements each binary signal of the previously complemented binary word representing the associated channel number.
Abstract:
A phase locked loop tuning system for a television receiver includes a voltage controlled local oscillator for generating a local oscillator signal corresponding to the channel presently selected by a viewer, a source of a reference frequency signal, a phase detector for generating pulses at the reference frequency the duration of which is a function of the phase and frequency relationship between the reference frequency signal and the local oscillator signal, and a low pass filter for deriving a D.C. control voltage for the voltage controlled oscillator from the output signal of the phase detector. The reference frequency is related to the horizontal and vertical television scanning rates in a predetermined manner so that undesired image components generated in response to unfiltered pulse components of the control voltage occurring at the reference frequency are substantially cancelled as an image is formed.
Abstract:
A commercial message timer stores data indicative of a first tuned station in response to a channel change command and begins repeatedly timing a predetermined time period. Upon each expiration of the time period, the user is reminded that the commercial message on the first tuned station may be over. In this way a user can avoid a commercial message on a first channel by setting the timer and scanning through other channels, and yet be reminded to return (e.g. by use of a PC (previous-channel) key) to the first channel at the end of a time period substantially equal to that of a typical commercial message. In another embodiment employing a videocassette recorder (VCR) the commercial timer is activated upon pressing the PAUSE key of the VCR so that the user may avoid recording the commercial message on videotape.
Abstract:
In automatic fine tuning (AFT) apparatus in a superheterodyne receiver, the IF carrier is selectively filtered and is applied to a signal multiplier arrangement. An auxiliary heterodyning signal is also applied to the multiplier arrangement, so as to produce an offset signal having a frequency proportional to the frequency difference between the IF carrier and the heterodyning signal. The offset signal is applied to a microprocessor programmed to produce a control signal for controlling the local oscillator to reduce frequency deviation between the IF signal and a nominal IF frequency.
Abstract:
A digital-to-analog converter suitable for use in a television tuning system for converting bits of a digital word to a corresponding tuning voltage includes a first digital-to-duty factor converter responsive to a group of the most significant bits of the digital word for generating a first incrementally variable duty factor pulse signal and a second digital-to-duty factor converter responsive to a group of the next most significant bits of the digital word for generating a second incrementally variable duty factor pulse signal. The amplitude of the first and second pulse signals are differentially weighted, e.g., by standard tolerance resistors (.+-.10%), such that the maximum average DC potential of the second signal is greater than a single increment of the average DC potential of the first signal. The weighted signals are combined and filtered by a lowpass filter which derives the tuning voltage. This deliberately results in non-monotonicity but without a significant reduction in resolution.
Abstract:
A microprocessor or other digital logic circuit recurrently tests the logical switching state of an input port. Based upon the outcome of such testing, the logical switching state at an output port is switched to the state opposite that of the input port. The recurrent testing develops at the output port a rectangular wave voltage that switches between upper and lower voltage levels. A filter coupled between the two ports develops at the input port a voltage representative of the average value of the output port voltage. The recurrent testing of the logical switching state of the input port produces a negative feedback of the output port voltage to the input port. The negative feedback develops a pulse-width modulated voltage at the output port that has an average value that is a multiple of the logic threshold voltage level of the digital logic circuit. To enable the digital logic circuit to perform a comparison of an analog voltage with a DC reference voltage, a second, comparison input port is coupled to the output port and is biased by the output port voltage at the logic threshold voltage level. The analog voltage and the DC reference voltage are then applied to the comparison input port. When the analog voltage exceeds the reference voltage, the voltage at the comparison port exceeds the logic threshold voltage level, resulting in the port being in a first logical switching state, and when the analog voltage is below the reference voltage, the voltage at the comparison port is below the logic threshold voltage level resulting in the input port being in the other logical switching state.
Abstract:
A servo system for a VideoDisc player stylus carrying carriage assembly is described which precludes the servo system entering a hunt mode due to the signal pickup stylus tracking an eccentric signal track. The player comprises a carriage for housing a track following signal pickup stylus compliantly mounted therein. A position detector generates an analog signal proportional to the stylus position relative to a relaxed or centered position. The position signal is converted to a bilevel signal (i.e. relatively positive and relatively negative levels), the two levels corresponding to the stylus being to the right or left of the centered position respectively. The bilevel signal is sampled at regular intervals, e.g. eight, per disc revolution. Counter circuitry counts the number of samples per disc revolution which are at the relatively positive level. The resulting number is examined to determine whether it is greater or lesser than one half the total number of samples per revolution and forward or backward control signals are generated respectively. The control signals are applied to a stepper motor coupled to the carriage for translating the carriage and thereby the stylus radially across the disc.