this is very common in homes built during the 50's and early 60's. the
actual wire is 3 conductor, however, the 'electricians' back then did not
fully understand the concept of alternate grounding. often, the ground wire
was cut, left coiled in the box and generally ignored as old stocks of 2
prong outlets got used up. dad told me that grounded outlets cost ten cents
and ungrounded were six.
Remember too that most builders back then were postmen, government clerks,
etc., that moonlighted as homebuilders when the need arose.
"Charlie" wrote in message
news:x6xhe.1354018$Xk.800039@pd7tw3no...
I've just come across about 3 or 4 wall outlets in my parent's home that
are
of the style that will only receive a male plug of 2 prongs. What is
involved in replacing the box innards with the receptacle that will take
the
male plug of 3 prongs (2 plus the third below and in the middle)? My
recollection from school days is that the major difference is the addition
of a ground wire to a screw in the middle of the receptacle. Or, am I
thinking of something altogether different. The rest of their house has
the
3 prong receptacles so this really is a bit of a mystery.

Charlie.