Question for the tech gurus (NMC)

[Tim2723]

On any number of AC power supplies that I use, including the computer I'm typing on now, there is a cylindrical component midway in the cable that connects the device to the AC/DC transformer. What is that? My usual 'wall wart' transformers have a plain wire making the connection, but these have this extra barrel-shaped device in-line.

[mclaugh]

It's a filter to reduce electromagnetic interference. You find them on switching power supplies, which generate a lot of high frequency noise. The usual wall warts you describe are linear power supplies that don't need that kind of filtering. The two types of supply are described (in great detail) at http://en.wikipedia.org/wiki/Switched-mode_power_supply

[Tim2723]

Thanks! That answers the question better than I needed to. I noticed that this type of power supply is attached to my more delicate electronics, like my computer and other things with lots of chips in them, while the normal wall wart is used in more robust applications.