| 摘要 |
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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