Acoustic telegraphy

As acoustic telegraphy (including harmonic telegraphy or Stimmgabeltelegrafie ) developed in the 19th century, various multiplexing methods are referred to, which made it possible to simultaneously transmit more than a telegraphic communication on a single telegraph line.

Procedures and history

At low frequencies the acoustic telegraphy or different communication channels are used for each message. A telegraph operator used here a conventional Morse key to tapping the message in Morse code. The key turned while a transfer of direct current pulses in the frequency deeper sound waves of a specific frequency or off. On the receiver side, there was a specially tuned device that resonated only at a specific resonance frequency and other transmitted over the same telegraph wire frequencies ignored.

The word comes from Greek acoustically ακουειν akuein "hear" from. The devices of the acoustic telegraphy worked electromechanical and caused more than a few meters audible humming or buzzing noise. However, the main function of this device was not the generation of sound waves, but the use of direct current pulses to the frequency of sound waves as a carrier signal for the Morse code.

Among the inventors who dealt with the acoustic telegraphy, including Charles Bourseul, Thomas Edison, Elisha Gray and Alexander Graham Bell. Your efforts to the development of acoustic telegraphy, which should reduce the cost of Telegrafiedienste, eventually led to the invention of the telephone.

Some of Thomas Edison's devices used multiple synchronized tuning forks that were tuned to select a frequency to open in this way an electrical circuit or close. The acoustic telegraphy was similar in concept to the present frequency division multiplexing.

Essential patents

  • AG Bell: Transmitter and Receiver for Electric Telegraphs. U.S. Patent 161739, April 6, 1875, PDF.
  • E. Gray: Electrical Telegraph for Transmitting Musical Tones. U.S. Patent 166095, July 27, 1875 PDF.
  • T. A. Edison: Acoustic Telegraph. U.S. Patent 182 996, October 10, 1876 PDF.
  • T. A. Edison: Acoustic Electric Telegraphs. U.S. Patent 186330, January 16, 1877, PDF.
  • T. A. Edison: Acoustic Telegraph. U.S. Patent 200993, March 5, 1878 PDF.
  • TA Edison: Circuits for Acoustic or Telephonic - Telegraphs. U.S. Patent 203019, April 30, 1878 PDF.
  • T. A. Edison: Acoustic Telegraph. U.S. Patent 235142, December 7, 1880, PDF.

Edison's patents were acquired by the Western Union Telegraph Company, based in New York City.

Evidence

  • Tom Standage: The Victorian Internet: The Remarkable Story of the Telegraph and the Nineteenth Century 's On -line Pioneers. Berkley Books, New York1998, ISBN 0-425-17169-8.
  • D. Robertson: The Great Mystery Telephone. In: IEEE Review. Volume 52, Number 2, 2006, pp. 44-48, DOI: 10.1049/ir: 20,060,204th
  • Brooke Clarke: Telephone patent, accessed on 29 July 2011.
Resonant frequency
38951
de