[Tfug] Why do they whine?

[erich]

OK,
        I went to the recent Worldcare outdoor sale, and bought a switch.
Brought it back home. Connected it to my system, and plugged it in to
TU Electric and noticed a whine. The whine is rather annoying when you're
trying to sleep. I've managed to reduce the sound somewhat.
        I noticed no ventilation holes in this thing, so the sound is
probably
not comming from a fan. What makes a switch whine?

                                                                                          
EWF