Radio scan controller?

[Paul Perry]

There are motorised pots (abt $10 or $15) which I suppose 
cd be the basis of something mechanical.
I think you have 2 pots on the shaft, one acts as a rotation
position sensor. They have a slipping clutch so you can 
override them by hand.
Really, it is the sort of thing the robotics hobbyists do
all the time, you'd be sure to get a response in their forums.

I'd use a midi-cv convertor (after all, I manufacture them!)
and have some kind of servo balancing against this... doubtless
there are many more elegant ways to do it.

paul perry Frostwave P/l melbourne Australia