Acoustic telegraphy (also known as harmonic telegraphy) was a name for various methods of
multiplexing (transmitting more than one)
telegraph
Telegraphy is the long-distance transmission of messages where the sender uses symbolic codes, known to the recipient, rather than a physical exchange of an object bearing the message. Thus flag semaphore is a method of telegraphy, whereas ...
messages simultaneously over a single
telegraph wire by using different
audio frequencies or
channels for each message. A telegrapher used a conventional
Morse key to tap out the message in
Morse code
Morse code is a telecommunications method which Character encoding, encodes Written language, text characters as standardized sequences of two different signal durations, called ''dots'' and ''dashes'', or ''dits'' and ''dahs''. Morse code i ...
. The key pulses were transmitted as pulses of a specific audio frequency. At the receiving end a device
tuned to the same frequency resonated to the pulses but not to others on the same wire.
Inventors who worked on the acoustic telegraph included
Charles Bourseul,
Thomas Edison
Thomas Alva Edison (February11, 1847October18, 1931) was an American inventor and businessman. He developed many devices in fields such as electric power generation, mass communication, sound recording, and motion pictures. These inventions, ...
,
Elisha Gray
Elisha Gray (August 2, 1835 – January 21, 1901) was an American electrical engineering, electrical engineer who co-founded the Western Electric, Western Electric Manufacturing Company. Gray is best known for his Invention of the telephone, dev ...
, and
Alexander Graham Bell
Alexander Graham Bell (; born Alexander Bell; March 3, 1847 – August 2, 1922) was a Scottish-born Canadian Americans, Canadian-American inventor, scientist, and engineer who is credited with patenting the first practical telephone. He als ...
. Their efforts to develop acoustic telegraphy, in order to reduce the cost of telegraph service, led to the
invention of the telephone.
[Standage, pp. 195–199]
Some of Thomas Edison's devices used multiple synchronized
tuning forks tuned to selected audio frequencies and which opened and closed electrical circuits at the selected audio frequencies. Acoustic telegraphy was similar in concept to present-day
FDMA, or frequency-division multiple access, used with radio frequencies.
The word ''acoustic'' comes from the Greek ''akoustikos'' meaning hearing, as with hearing of sound waves in air. Acoustic telegraphy devices were electromechanical and made musical or buzzing or humming sound waves in air for a few feet. But the primary function of these devices was not to generate sound waves, but rather to generate alternating electrical currents at selected audio frequencies in wires which transmitted telegraphic messages electrically over long distances.
Patents
* – ''Improvement in Transmitters and Receivers for Electric Telegraphs'' – Alexander Graham Bell, issued April 6, 1875
* – ''Electrical Telegraph for Transmitting Musical Tones'' – Elisha Gray, issued July 27, 1875
Reissue # 8559Jan. 28, 1879
* – ''Improvement In Electro-Harmonic Telegraphs'' – Elisha Gray, issued February 15, 1876
* – ''Acoustic Telegraph'' – Thomas Edison, issued October 10, 1876
* – ''Improvement in electro-haronic multiplex telegraphs'' – Thomas Edison, issued December 19, 1876
* – ''Acoustic Electric Telegraphs'' – Thomas Edison, issued January 16, 1877
* – ''Acoustic Telegraphs'' – Thomas Edison, issued March 5, 1878
* – ''Circuits for Acoustic or Telephonic Telegraphs'' – Thomas Edison, issued April 30, 1878
* – ''Acoustic Telegraph'' – Thomas Edison, issued December 7, 1880
The five Edison patents were assigned to
Western Union Telegraph Company of New York.
See also
*
Telegraph
Telegraphy is the long-distance transmission of messages where the sender uses symbolic codes, known to the recipient, rather than a physical exchange of an object bearing the message. Thus flag semaphore is a method of telegraphy, whereas ...
*
Invention of the telephone
References
;Notes
;Bibliography
* Standage, Tom, ''The Victorian Internet'',
Berkley Books, New York (Penguin), 1998,
* D. Robertson
''The Great Telephone Mystery'' IEEE Review, Feb. 2006, Volume: 52, Issue: 2, pp. 44– 48, , INSPEC Accession Number: 8770451, Current Version Published: 2006-02-27.
* Brooke Clarke
''Telephone Patents''
{{DEFAULTSORT:Acoustic Telegraphy
Telegraphy
Multiplexing