| 摘要 |
PURPOSE:To realize an automatic channel selection circuit tuned completely by one-motion while using a signal whose frequency voltage characteristic is of the S shaped type, by combining a charge/discharge circuit, a flip-flop circuit and an up/down switch. CONSTITUTION:An input stage 2 receiving signals showing S-shaped characteristic near the tuning point and forming signals of rectangular characteristic, a flip-flop circuit 3, a charge/discharge circuit 6 to form a channel selection voltage, a turning scan up-switch 4 and a down-switch 5 are provided. The flip-flop circuit 3 is set to a state or other state in response to the operation of the up/down switches 4, 5 and the charging/discharging is switched to the charge/discharge circuit 6 depending on the state of an output SF of the flip-flop circuit 3. Then the signal from the input stage 2 is supplied to one input of the flip-flop circuit 3 with the same polarity and fed to the other input terminal while being inverted as the trigger signal. Thus, the tuning is applied automatically and since the automatic tuning utilizes the signals of S-shaped characteristic, the complete tuning is attained.
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