Spring Line Hum

[Paul Perry]

At 09:25 PM 17/07/00 -0600, Ian Fritz wrote:
>Once again I remind you all that springs operate in a torsional mode. How,
>exactly, would you make an optical pickup?
>
Why, with a shaped piece of metal foil attached at rightangles to the 
spring, so that as the spring rotates about its axis, it occludes
more or less of the light in a beam perpendicular to it.
The same way an optical footpedal works.

paul perry Melbourne Australia