| 摘要 |
A teletext data separation apparatus has a slice level generating circuit including a slice timing control circuit, a control register, an adder and a divider. The slice timing control circuit generates a timing signal for sampling. The control register carries out ON/OFF control of the slice timing control circuit. The control register sets by its register value the number of the sampling points of the adder and divider. By varying the register value in response to the reception state, the number of the sampling points can be increased from the specified 16 points, for example. This makes it possible for teletext data separation apparatus to generate an appropriate slice level that enables the teletext data to be separated reliably even in conditions where noise or distortion occurs in the video signal because of the effect of a weak electric field or ghost.
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