Acoustic telegraphy (also known as harmonic telegraphy) was a name for various methods of
multiplexing
In telecommunications and computer networking, multiplexing (sometimes contracted to muxing) is a method by which multiple analog or digital signals are combined into one signal over a shared medium. The aim is to share a scarce resource - a ...
(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 p ...
messages simultaneously over a single
telegraph wire by using different
audio frequencies
An audio frequency or audible frequency (AF) is a periodic vibration whose frequency is audible to the average human. The SI unit of frequency is the hertz (Hz). It is the property of sound that most determines pitch.
The generally accepted ...
or
channels
Channel, channels, channeling, etc., may refer to:
Geography
* Channel (geography), in physical geography, a landform consisting of the outline (banks) of the path of a narrow body of water.
Australia
* Channel Country, region of outback Austral ...
for each message. A telegrapher used a conventional
Morse
Morse may refer to:
People
* Morse (surname)
* Morse Goodman (1917-1993), Anglican Bishop of Calgary, Canada
* Morse Robb (1902–1992), Canadian inventor and entrepreneur
Geography Antarctica
* Cape Morse, Wilkes Land
* Mount Morse, Churc ...
key to tap out the message in
Morse code
Morse code is a method used in telecommunication to encode text characters as standardized sequences of two different signal durations, called ''dots'' and ''dashes'', or ''dits'' and ''dahs''. Morse code is named after Samuel Morse, one ...
. 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
Charles Bourseul (28 April 1829 – 23 November 1912) was a pioneer in development of the "make and break" telephone about 20 years before Bell made a practical telephone.
Bourseul was born in Brussels, Belgium, and grew up in Douai, Franc ...
,
Thomas Edison,
Elisha Gray
Elisha Gray (August 2, 1835 – January 21, 1901) was an American electrical engineer who co-founded the Western Electric Manufacturing Company. Gray is best known for his development of a telephone prototype in 1876 in Highland Park, Illinois ...
, and
Alexander Graham Bell
Alexander Graham Bell (, born Alexander Bell; March 3, 1847 – August 2, 1922) was a Scottish-born inventor, scientist and engineer who is credited with patenting the first practical telephone. He also co-founded the American Telephone and T ...
. Their efforts to develop acoustic telegraphy, in order to reduce the cost of telegraph service, led to the
invention of the telephone
The invention of the telephone was the culmination of work done by more than one individual, and led to an array of lawsuits relating to the patent claims of several individuals and numerous companies.
Early development
The concept of the ...
.
[Standage, pp. 195–199]
Some of Thomas Edison's devices used multiple synchronized
tuning fork
A tuning fork is an acoustic resonator in the form of a two-pronged fork with the prongs ( tines) formed from a U-shaped bar of elastic metal (usually steel). It resonates at a specific constant pitch when set vibrating by striking it against ...
s 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
Frequency-division multiple access (FDMA) is a channel access method used in some multiple-access protocols. FDMA allows multiple users to send data through a single communication channel, such as a coaxial cable or microwave beam, by dividing ...
, 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
* – ''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
The Western Union Company is an American multinational financial services company, headquartered in Denver, Colorado.
Founded in 1851 as the New York and Mississippi Valley Printing Telegraph Company in Rochester, New York, the company chang ...
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 p ...
*
Invention of the telephone
The invention of the telephone was the culmination of work done by more than one individual, and led to an array of lawsuits relating to the patent claims of several individuals and numerous companies.
Early development
The concept of the ...
References
;Notes
;Bibliography
* Standage, Tom, ''The Victorian Internet'',
Berkley Books
Berkley Books is an imprint of the Penguin Group.
History
Berkley Books began as an independent company in 1955. It was founded as "Chic News Company" by Charles Byrne and Frederick Klein, who had worked for Avon; they quickly renamed it Berk ...
, 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''
Telegraphy
Multiplexing
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