http://www.hometoys.com/htinews/apr98/articles/kingery/kingery8.htm
Here's a link, check fig#7... looks like what's being described ( Bordew, I get these links from the BB's, just obligated to pass them on...)

I would think your best( Nec Legal) option for only a 3 -wire would be automation ( X-10) controls.
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