laptop ACadapter barrel plug polarity simbol?

What's the barrel plug symbol means when it has a solid line on top and a dashed right under it? Is that ot say the barrel plug has the inside cylinder as negative and the outside positive? or is it hte other way around?

Neither. IIRC it means the input needs to be *regulated* DC power (not a wall wart).

Usually there's another indicator like a C with a dot in the middle (i.e., the end of a barrel connector), with one of them showing + or -. That's your polarity marking.

Richard

Should've said "most" wall warts. Nearly all the wall warts I come across (i.e., consumer goods) aren't regulated, though there are certainly exceptions like the one you mentioned. (IME most regulated supplies tend to be inline bricks for some reason, like laptops.)

Cheers, Richard

Hey - some wall warts *are* regulated DC.

Did you mean 'it isn't AC' ?

Graham