diac-triac, extended range, full-wave phase control circuit for inductive loads

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Original poster: "michael curtiss" <lucknau-at-yahoo-dot-com> 




I found variations of this circuit in several places
online and in print, and am wondering if its an
acceptable phase control circuit for an SRSG:


http://www.geocities-dot-com/lucknau/diac-triac_phase_control.jpg

It uses a variable resistor to control phase, instead
of a variac, as in John Freau's schematic:

  http://hometown.aol-dot-com/futuret/images/phshift4.jpg