The 'doughnut' (or 'special panning module' control) was built for Starlight Express and was used manually by the operator to pan effects around the auditorium during the races.
The large dial was located on the surface between the custom-built Cadac mixer sections which contained a light source and a series of light sensors around it, which ramped the audio up and down in a series of speakers around the auditorium in response to the brightness of the light.

Starlight Doughnut Panning Control
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Starlight Doughnut Panning Control underside
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