> Is it O for On, or O for Off? I never remember.

Does it matter? You know it means either on or off, and you know whether it's already on or off... I haven't seen anyone struggle to figure out what happens given these two pieces of information?

Sometimes equipment isn't obviously on or off. Like the main switch on a power supply. I also like to know that something is off when I try to plug it in (like the table saw).

I thought we're talking about cars? I never claimed all standardized icons for all equipment are intuitive.

Ok, cars. How do you know the electric wires for the defroster are on or off? I can't see electric fields. You can wait 10 minutes and see if it defrosts I suppose. I don't see that as an improvement on phonetic writing.

There's a light that turns on?

Not always.

Well that's the problem then, not the icon...

Umm, it's binary. 1=on,0=off.