| 摘要 |
<p>A digital teletext signal is transmitted during part of a vertical blanking period of a television signal. A clock oscillator synchronized by the teletext signal is coupled to a synchronizing input of a logic circuit providing clock and data signals for teletext processing. To prevent high harmonics that are included in the clock and data signals from producing interference within the reproduced picture, the amplitude of an output signal of the clock oscillator is reduced, during vertical trace, when the teletext signal is not transmitted to prevent switching operations in the logic circuit.</p> |
