The picture elements across a line are converted to the video signal and low-pass filtered with an electrical filter .

沿着一条直线的图象象素被转换成视频信号，然后由一个电子滤波器进行低通滤波。

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For a low-pass filter, signals much longer than the time constant pass through unaltered while signals shorter than the time constant are filtered out.

对于低通滤波器，比时间常数更长的信号将会保持不变地通过，而比时间常数短的信号将会被滤掉。

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