Quasar Electronics Corporation

David J Mueller

Hugh F Bonney

An electronic tuner control system particularly adapted for television receivers employs a gated oscillator for sequentially stepping the tuner from one channel selection to the next. The system includes a counter responsive to the gated oscillator for causing the sequential scanning or stepping to take place in either the 'up' or 'down' direction. Separate tuning potentiometers are associated with each channel and are selected in sequence under control of the counter. Each potentiometer is set to either a first range of settings indicative of a valid tuning voltage for that channel or to a second range indicating that no tuning or channel selection is to be effected for such a second or 'non-preferred' setting. All of the tuning potentiometers are coupled to an analog steering circuit comprised of isolating diodes, and only one potentiometer at a time is selected to apply a tuning voltage to the output of the steering circuit under control of the counter. The output voltage from the analog steering circuit comprises the tuning voltage supplied to the electronic tuners of the receiver, and this voltage also is sensed by an override circuit which automatically causes the oscillator to operate at a high frequency to effectively skip over the 'non-preferred' channels. When a channel which has a valid tuning voltage on it is selected, the override circuit causes the oscillator to operate at a lower frequency to give the operator of the tuning system an opportunity to de-energize or release the control circuit to stop on the selected channel. If the control circuit is released or de-energized when the oscillator is operating in its higher frequency, it continues to operate until a channel with a valid tuning voltage is selected, whereupon further scanning terminates.

Electronic tuner control system

An automatic fine tuning defeat circuit disables the application of an automatic fine tuning or automatic frequency control correction voltage to the voltage-controlled tuners of a television receiver during switching from one channel to another. The tuning voltage for a selected channel is coupled in series with the automatic frequency control voltage to provide a composite tuning voltage for the tuners. During a channel change, a switch is rendered conductive to shunt or short-circuit the output of the automatic frequency control circuit, thereby rendering its output ineffective for control of the tuners during channel change. Upon completion of the channel change, the automatic frequency control circuit output voltage again is applied in series with the tuning voltage to form the composite tuning voltage for the tuners.

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Northlake, IL, United States of America

David J Mueller