Berliner's Variable Contact Microphone

Title

Berliner's Variable Contact Microphone

Source

https://www.google.com/patents/US463569?dq=emile+berliner+1877&hl=en&sa=X&ved=0ahUKEwi4qf3-6rXRAhVGQyYKHUefBV4Q6wEIGzAA

Contributor

rah

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