On Thu, 19 Apr 2007 12:07:25 -0700, Jim Thompson
wrote:


output with the turn of a dial.

I have been "backstage" for at least 40 years. Back then I recall
big-ass chokes with a moveable core to change the inductance.

...Jim Thompson

And the big 'board' with many knobs to adjust lights... g Whether an
adjustable inductor, or a Variac, those things were big--lot's of
power involved.