A former manufacturer of stage lighting and control systems based in Salt Lake City, UT and Calgary, Alberta, Canada. Formed in 1964 by a hostile takeover/buyout of Ariel Davis Manufacturing Company (see Note1 below), and purchased by Strand in 1986. The Salt Lake City factory closed in 1991. While never a top-tier manufacturer, they did have a large portion, if not the majority, of the educational market share in the 1970s and early 80s.
Their most memorable product is likely the Parellipshere, a profile spotlight introduced in the 1970s and somewhat ahead of its time, featuring a computer-designed hybrid parabolic-ellipsoidal-spherical (hence the name) glass reflector and other features that would not appear on other fixtures until many years later.
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More information at The Electro Controls Archive http://electrocontrolsarchive.blogspot.com/. No relation to the similarly-named current company, http://electrocontrols.com/, which makes HVAC control and building management systems.
Note1: From http://mentorseries.blogspot.com/ :