I have a question that maybe an engineer could answer. The voltage adaptor that came with my portable phone (Ericsson) in order to recharge its batteries made me wonder a lot. It is very small, about the size of a matchbox, and yet not much heavier. It's hard to believe that there's a coil with an iron core hidden inside, as in a standard voltage transformator. I also noticed that normal trafo's get warm simply if they're plugged in (and not in use) as a result of the ohm resistance (or whatever the word is) of the coil - this one doesn't. Can anyone explain to me what technique is used here?