A quick follow on question,

        I seem to remember a device which allow one to apply some
percentage of the AC waveform similar to pulse width modulation.  That
is:
        full power = full waveform
        half power = 180 degrees of waveform
        X% power   = appropriate % of the waveform

I do not remember what that device is.  Any help?

Thanks Markus for your quick reply.

Martin Kirk
Arizona State University
mlk@asu.edu
(602) 263-9270