I have a 901 here... I saw some basic info on how it's done in the user's guide, but that's all.
Do you have that? how much info do you need?" -Basically the "how-it-works" or are you looking for component values so you can repair or even clone one?
BTW, once you get how it's done, it's an easy matter to take something like the amek 2500 SVF EQ and add a few detectors and 2180 type VCAs and you're good to go.
...it's not much of an effort, since we just installed a scanning photocopier with on-board email here at work... (scans each page in under a second and emails it out before I can get back to my desk, 10 feet away!)