| 摘要 |
A television signal seeking system includes a UHF tuner driven by a bidirectional motor. The motor windings are energized through transistor switching circuits which are coupled to signal sensing circuits. Once the motor switch circuits are actuated the motor will drive the tuner through the television frequency spectrum until a stopping signal is applied to the motor switch circuits to deenergize the motor. The stopping signal is developed in response to (1) the presence of a train of horizontal sync pulses; (2) the presence of a predetermined level of automatic gain control voltage; and, (3) the presence of a change of automatic fine tuning correction voltage, when the tuning elements are driven into the pull-in range of the automatic fine tuning circuits.
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