Thank you. I read it with interest. Brought back many memories. I used to save porcelain knobs and cotton loom for repairs to knob and tube...those were mostly 30 amp branch circuits then and sometimes the grounded tap conductors were run from underneath the rooms and the ungrounded taps were dropped down from above. Many were originally supplied by village-owned motor driven DC generators before A/C distribution reached their towns. Greenfield village at the Detroit Ford Motor Company Hqtrs. has some of Edison's labratory and office on display. Originally he stretched bare (#12 ?) copper spaced about 4" apart and secured to wooden blocks about every 4ft. as insulators. I believe that he invented the tungsten filament lamp as well. Later conversion of steel pipe for gaslights was adapted for what we now call conduit...must have had some sharp edges...