Cambridge Instruments Slide-Wire Potentiometer

[Paula A]

I can think of a use right off the bat.. calibrating Avo's .. it was common to stick the carbon rod resistances across a bridge containing one of these things when they were being filed down (up?) to a precise value. Another use I can think of is calibrating oscillators.

http://www.lhup.edu/~dsimanek/scenario/l...wheats.htm