You need DPST switches in much of Europe because there
you find
unpolarized outlets.
And because in some parts of Europe you find balanced mains,
rather
than hot-and-neutral mains.
I don't think so. In Europe, plain old home
service is 220 volts
live to neutral.
This depends on where in Europe. Most of Europe is, I understand, as
you describe, but the part of Norway I was in (Troms?) certainly used
balanced (or at least approximately balanced) mains, and I'm told it's
usual in the rest of Norway too. There may be other such areas, though
I don't know of any specific examples.
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