Multiturn Potentiometers

Some articles on potentiometers:

Riostat - Potentiometer Construction
... Potentiometers comprise a resistive element, a sliding contact (wiper) that moves along the element, making good electrical contact with one part of it, electrical terminals ... Many inexpensive potentiometers are constructed with a resistive element formed into an arc of a circle usually a little less than a full turn, and a wiper rotating around the arc ... On panel potentiometers, the wiper is usually the center terminal of three ...