Hammond delay thingie (was: mysterious delay lines)

[Hcabnivek at aol.com]

Speaking of delay like devices  (though I'm not sure this real is one) can
someone explain how the small motor driven drum inside a Hammond organ that
has all the wires connected to it works to generate tremolo/varabrato.  I'm
not talking about a Leslie here, this thing has a wire from each of the draw
bars connected to it I guess a single output wire, and some rotating part
inside that's turned by a belt running off the same motor that turns the tone
wheels.
Anyone?
Kevin