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Author
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Topic: help needed with PR1F motor rewind (HFC)
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Jim Cassedy
Phenomenal Film Handler
![](http://www.film-tech.com/ubbmembers/4115a.jpg)
Posts: 1661
From: San Francisco, CA
Registered: Dec 2006
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posted 04-21-2016 02:35 PM
quote: Tony Bandiera Jr Earlier sewing machines' foot pedals were simply a rheostat of nichrome wire with multiple contact taps
Many years ago I fixed my mom's 1940's vintage Singer sewing machine, and it used a "carbon-pile" speed control footswitch.
Inside, a number of carbon/graphite disks, each a little larger than a dime, were loosely contained inside a ceramic insulator tube with metal contacts at each end. (Think of a paper roll of dimes you'd get at the bank)
Stepping on the footswitch compressed the disks together. The more they were compressed, the lower the resistance, and the faster the motor ran. Eventually, if you continued stepping down harder on the footswitch, you'd reach a spot where a set of metal contacts would bypass the carbon pile entirely, & the motor would run at full speed.
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