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The Phonophor was the first heating aid from Siemens & Halske. Like telephones, electric hearing aids are based on converting acoustic vibrations into electrical voltage fluctuations, amplifying them, and then converting them back. The Phonophor was sold starting in 1913, in several versions, including a ladies’ model with the microphone and battery built into a purse.
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- Friday 15 March 2019
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