Carbon Telephone Transmitter

In 1876, Edison began work to improve the microphone for telephones (at that time called a "transmitter") by developing a carbon microphone that used a button of carbon that would change resistance with the pressure of sound waves. Up to that point, microphones, such as the ones developed by Johann Philipp Reis and Alexander Graham Bell, worked by generating a weak current. Edison was one of many inventors working on the problem of creating a usable microphone for telephony by having it modulate an electrical current passed through it. His work was concurrent with Emile Berliner's loose-contact carbon transmitter (who lost a later patent case against Edison over the carbon transmitters invention) and David Edward Hughes study and published paper on the physics of loose-contact carbon transmitters (work that Hughes did not bother to patent).

Edison used the carbon microphone concept in 1877 to create an improved telephone for Western Union. In 1886, Edison found a way to improve a Bell Telephone microphone, one that used loose-contact ground carbon, with his discovery that it worked far better if the carbon was roasted. This type was put in use in 1890 and was used in all telephones along with the Bell receiver until the 1980s.

• Outline of Thomas Edison (1847-1931)
  

  HISTORIC PEOPLE

  Thomas Edison (1847-1931)

  Thomas Edison was an American inventor and businessman, who has been described as America's greatest inventor. He developed many devices that greatly influenced life around the world, including the phonograph, the motion picture camera, and the long-lasting, practical electric light bulb. View Thomas Edison (1847-1931) »

  Early Life: Edison only attended school for a few months and was instead taught by his mother. Much of his education came from reading R.G. Parker's School of Natural Philosophy and The Cooper Union for the Advancement of Science and Art.

  Telegrapher: In 1866, at the age of 19, Edison moved to Louisville, Kentucky, where, as an employee of Western Union, he worked the Associated Press bureau news wire.

  Beginning his Career: Edison began his career as an inventor in Newark, New Jersey, with the automatic repeater and his other improved telegraphic devices, but the invention that first gained him wider notice was the phonograph in 1877.

  Research and Development Facility: Edison was legally attributed with most of the inventions produced there, though many employees carried out research and development under his direction.

  Carbon Telephone Transmitter: Edison used the carbon microphone concept in 1877 to create an improved telephone for Western Union.

  Electric Light: After many experiments, first with carbon filaments and then with platinum and other metals, Edison returned to a carbon filament.

  Electric Power Distribution: Edison switched on his Pearl Street generating station's electrical power distribution system, which provided 110 volts direct current (DC) to 59 customers in lower Manhattan.

  Final Years: Edison was impressed with Ford's internal combustion engine automobile and encouraged its developments.

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This article uses material from the Wikipedia article "Thomas Edison (1847-1931)", which is released under the Creative Commons Attribution-Share-Alike License 3.0.