| 摘要 |
The TV receiver employs a synchronous video detector system, and includes an AFT detector responsive to carrier waves supplied by a reference amplifier of the synchronous detector system. A peak detector, independent of the synchronous video detector and the receiver's AGC system, is responsive to the output of the receiver's IF amplifier, and supplies an output to a voltage comparator. When the comparison indicates the IF output swing exceeds a threshold value, the AFT detector is disabled to avoid an AFT lock out condition, which may occur owing to the production of beat frequencies in certain off-turned conditions.
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