Parts of this Metropolis are wired in old heavy wall flex, '50 - '75, (1975 was when the "all metal" local code was relaxed to allow NM, and I have found numerous hallway / stairway installations of this 4 - wire setup in high end homes.
When I was apprenticing I was taught this 4 -wire arrangement was called a "California Threeway".
Anyone got other names for it, or for that matter, the true meaning of California Threeway if this is not it?
Al
