Automatic fine tuning defeat circuit
AssigneeQuasar Electronics Corporation
InventorDavid J. Mueller
Life of this patent
Estimating the term…
Abstract
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.
Claims12
A system for a wave signal receiver including in combination:
- a voltage responsive tuner stage tunable to different frequencies within at least one band of frequencies in response to a tuning voltage applied thereto;
- automatic frequency control means coupled with the output of said tuner stage for producing an automatic frequency control voltage indicative of the tuning of said tuner stage;
- tuning voltage supply means for supplying a voltage;
- means for coupling said tuning voltage supply means and the output of said automatic frequency control means to said voltage responsive tuner stage to supply said tuning voltage thereto, said tuning voltage being a composite of the voltage supplied by said tuning voltage supply means and the automatic frequency control voltage from said automatic frequency control means;
- and
- switch means coupled to said automatic frequency control means and to said tuning voltage supply means for sensing a predetermined voltage supplied by said tuning voltage supply means, said switch means being operative in response to said predetermined voltage to remove the effect of said automatic frequency control voltage from said composite tuning voltage.
In a television receiver, a system including in combination:
- a voltage responsive tuner stage tunable to different frequencies within at least one band of frequencies in response to a tuning voltage applied thereto;
- an automatic frequency control circuit including a discriminator having first and second output terminals floating with respect to ground for producing across such output terminals an automatic frequency control voltage having a magnitude and polarity indicative of the tuning of said tuner stage;
- tuning voltage supply means coupled to one of the output terminals of said automatic frequency control circuit, the other output terminal of said automatic frequency control circuit coupled to said tuner stage, forming a series circuit supplying said tuning voltage to said tuner stage, said tuning voltage being a composite of a voltage supplied by said tuning voltage supply means and said automatic frequency control voltage from said automatic frequency control circuit;
- a normally nonconductive transistor switch, the emitter-collector path of which is connected across said first and second output terminals of said discriminator and the base of which is coupled to the output of said tuning voltage supply means for sensing a predetermined voltage supplied thereby, said transistor switch rendered conductive in response to said predetermined voltage to shunt the output terminals of said automatic frequency control discriminator, rendering the automatic frequency control voltage ineffective while said transistor switch is conductive.
Dependencies are inferred from the claim text.