Hearing aid patent from 1939
One of the most successful categories of electronic wearable devices is one that most people never think of - hearing aids. This patent was filed in 1939 and features a wearable bone-conduction hearing aid.
U.S. Patent number: 2249572
Filed: March 22, 1939
Publication date: July 15, 1941
Assignee: Dora Lieber, Lieber Patents Corp.
Image taken from U.S. Patent 2249572 - Digitized by Google
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