Experimental carbon block microphone, 1878-1890

Experimental microphone having two carbon blocks contained in a Experimental carbon block microphone, 1878-1890 Experimental microphone having two carbon blocks contained in a

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Creative Commons LicenseThis image is released under a CC BY-NC-SA 4.0 Licence

Buy this image as a print 

Buy

License this image for commercial use at Science and Society Picture Library

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Creative Commons LicenseThis image is released under a CC BY-NC-SA 4.0 Licence

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License this image for commercial use at Science and Society Picture Library

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Experimental microphone having two carbon blocks contained in a
Science Museum Group Collection
© The Board of Trustees of the Science Museum

Science Museum Group Collection
© The Board of Trustees of the Science Museum

Experimental microphone having two carbon blocks contained in a
Science Museum Group Collection
© The Board of Trustees of the Science Museum

Experimental microphone having two carbon blocks contained in a glass tube and pressed together by a spring, probably made by David Edward Hughes, England, 1878-1890.

The development of the microphone owes much to David Edward Hughes (1831-1901). Building on the work of Willoughby Smith and Sir William Thomson, Hughes attempted to detect changes in the resistance of wire with sound. He discovered that these changes occurred only when his stretched test wire broke and when he touched the ends together. He found that light but constant pressure was the only essential and in this experiment the pressure of two carbon blocks is maintained by a spring. Hughes did not patent his discoveries, meaning that subsequent inventors were able to make use of them without giving Hughes the credit.

Details

Category:
Telecommunications
Object Number:
1922-153
Materials:
plastic (unidentified), copper (alloy) and wax
Measurements:
overall: 100 mm x 15 mm diameter, .01 kg
type:
microphone
credit:
Executors of the late Anna C. Hughes