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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This is possible using algorithms that filter out interference caused by external electrical activity.

ECONOMIST: Brainwave controllers

They have long been employed in devices like mobile phones to filter electric signals (which can be done by converting electrical into mechanical energy and back again).

ECONOMIST: Acoustic microfluidics