91
Power socket types around the world
(upload.wikimedia.org)
For the map enthused!
Rules:
post relevant content: interesting, informative, and/or pretty maps
be nice
Are devices generally interoperable?
These days, yes. Older devices were usually only made for one frequency or the other. Clocks, for example, would not keep time correctly if they were using the cycles as a way to count time and were used in the opposite area for which they were designed.