This is indeed a variable autotransformer (a D-2000) manufactured by the Superior Electric Co. - in wiring, it's coil is connected between a hot leg and neutral, and a sliding contact taps off the desired load voltage. It can handle any load up to its maximum rating of about 2000 watts. I've also seen these in use in many locations - theater stage lighting switchboards with a rack and pinion gear operating mechanism, single dimmers such a this one with a large operating knob, and single and multiple (stacked) models operated with a gear-reduction electric motor from a remote location. Our community theater here uses two of these D-2000's to control the auditorium lights, operated by a pair of momentary contact SPDT switches backstage and in the lighting/sound control room.
Mike (mamills)
[This message has been edited by mamills (edited 05-07-2006).]
