"Geoffrey S. Mendelson" wrote in message
...

snip
: The UK used several systems, and a friend of mine who traveled
to London
: in the 1970's found that there were four different electrical
systems in use
: in various parts of the city. By that time they had been
standardized to
: 240 volts 50Hz, but the older plugs and lightbulbs (different
ones for
: different systems) remained.

Hmm, surely the 1970s were a tad late for different voltages
(certainly for London), the national grid had been started long
before WW2 and was complete not long after, are you are not
thinking of the different designs of electrical circuits and
sockets in use or perhaps a different time period?

I suppose that some building with their own (derived/generated)
power supplies might have had (still have) 'odd' systems to suit
their own needs, an exception rather than the rule.
--
Regards, Jerry.