File: US Patent 3118022 - Gerhard M. Sessler James E. West - Bell labs - electroacustic transducer - foil electret condenser microphone 1962 1964 - pages 1-3.png

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current05:50, 13 January 2009Thumbnail for version as of 05:50, 13 January 20093,964 × 1,958 (207 KB)Lloyd Pumphrey (talk | contribs)Imported from Wikipedia

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