envelope generators

[K.Dunnicliffe at uk22p.bull.co.uk]

> Yup, I recall hearing about knobs that would close a contact repeatedly
> if you spun them to the left, and close another contact if you spun them 
> to the right.  One full turn would trigger the thing maybe 60 times.  The 
> faster you turn, the faster the contact is switched on and off.  Perfect 
> for driving a digital increment/decrement-by-one circuit.  Remember the
> video game "tempest"?

This made me think - Many mice (the computer sort) have optical encoders 
that do exactly this sort of thing. The components for this ought to be 
very cheap due to the vast quantities of mice everywhere.
Hey, I probably have a couple of dead rodents in a drawer I could play
with ...

Kevin.