19. Applications of Switch

Question.4

On the red power switch of the extension box in the picture, you see two symbols: a straight line (I) and a circle (O). What do these two symbols mean for the flow of electricity in the extension box?

I stands for "Increase" and O stands for "Overload."
They are universal binary symbols (1 and 0) that everyone in the world can understand.
I stands for "Input" and O stands for "Output" of electricity.
The letters are just used to help the plastic grip your finger better.

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