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  Publications

  The Bulletin Index: Pittsburgh's Weekly Newsmagazine, December 28, 1939

  • The Bulletin Index: Pittsburgh's Weekly Newsmagazine, Volume 115, Number 26

  • 1939-Dec-28

  Front page and page 6 of the December 28, 1939 issue of the Bulletin Index: Pittsburgh's Weekly Newsmagazine. The article on the top left, titled "Warfare Waste," features Ernst Berl (1877-1946) discussing ammunition…

  • Publisher Bulletin-Index Co.
  • Subject Berl, Ernst, 1877-1946, World War (1914-1918), Ammunition, American periodicals--Foreign language press, Newspapers, Pennsylvania--Pittsburgh
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  Photographs

  Helipot Model 5533 Single-Turn Wirewound Potentiometer with Cartridges

  • 1950 – 1969

  Potentiometers regulate the flow of electricity, like the volume dial on a radio. In 1940, Arnold O. Beckman was unsatisfied with dials on the market, so he designed his own helical potentiometers, or helipots, for use…

  • Photographer Armstrong & Hess
  • Subject Cartridges, Potentiometer, Beckman Instruments, Inc., Ammunition