Telecommunication is the exchange of information by various types of technologies
over wire, radio, optical or other electromagnetic systems.[1][2] It has its origin in the desire of humans
for communication over a distance greater than that feasible with the human voice, but with a similar
scale of expediency. This excludes systems such as postal mail from the field of telecommunication.
The Latin term communicatio is considered the social process of information exchange, and the
Greek prefix tele expresses distance.
The transmission media in telecommunication have evolved through numerous stages of technology
from beacons and other visual signals, such as smoke signals, semaphore telegraphs, signal flags,
and optical heliographs, to electrical cable and electromagnetic radiation, including light. Such
transmission paths are often divided into communication channels which afford the advantages
of multiplexing multiple concurrent communication sessions. Telecommunication is often used in its
plural form, because it involves many different technologies.[3]
Other examples of pre-modern long-distance communication included audio messages such as
coded drumbeats, lung-blown horns, and loud whistles. 20th- and 21st-century technologies for long-
distance communication usually involve electrical and electromagnetic technologies, such
as telegraph, telephone, television and teleprinter, networks, radio, microwave transmission, optical
fiber, and communications satellites.
A revolution in wireless communication began in the first decade of the 20th century with the
pioneering developments in radio communications by Guglielmo Marconi, who won the Nobel Prize
in Physics in 1909, and other notable pioneering inventors and developers in the field of electrical
and electronic telecommunications. These included Charles Wheatstone and Samuel
Morse (inventors of the telegraph), Alexander Graham Bell (inventor of the telephone), Edwin
Armstrong and Lee de Forest (inventors of radio), as well as Vladimir K. Zworykin, John Logie
Baird and Philo Farnsworth (some of the inventors of television).
Contents
1Etymology
2History
o 2.1Beacons and pigeons
o 2.2Telegraph and telephone
o 2.3Radio and television
o 2.4Thermionic valves
o 2.5Semiconductor era
2.5.1Transistors
2.5.2Computer networks and the Internet
2.5.3Wireless telecommunication
2.5.4Digital media
o 2.6Growth of transmission capacity
3Technical concepts
o 3.1Basic elements
o 3.2Analog versus digital communications
o 3.3Communication channels
o 3.4Modulation
o 3.5Telecommunication networks
4Societal impact
o 4.1Microeconomics
o 4.2Macroeconomics
o 4.3Social impact
o 4.4Entertainment, news, and advertising
5Regulation
6Modern media
o 6.1Worldwide equipment sales
o 6.2Telephone
o 6.3Radio and television
o 6.4Internet
o 6.5Local area networks and wide area networks
7See also
8References
o 8.1Citations
o 8.2Bibliography
9External links
Etymology[edit]
The word telecommunication is a compound of the Greek prefix tele (τηλε), meaning distant, far off,
or afar,[4] and the Latin communicare, meaning to share. Its modern use is adapted from the French,
[5]
because its written use was recorded in 1904 by the French engineer and novelist Édouard
Estaunié.[6][7] Communication was first used as an English word in the late 14th century. It comes from
Old French comunicacion (14c., Modern French communication), from Latin communicationem
(nominative communicatio), noun of action from past participle stem of communicare "to share,
divide out; communicate, impart, inform; join, unite, participate in", literally "to make common", from
communis".[8]
History[edit]
Further information: History of telecommunication
Beacons and pigeons[edit]
A replica of one of Chappe's semaphore towers
Homing pigeons have occasionally been used throughout history by different cultures. Pigeon
post had Persian roots, and was later used by the Romans to aid their military. Frontinus said
that Julius Caesar used pigeons as messengers in his conquest of Gaul.[9] The Greeks also
conveyed the names of the victors at the Olympic Games to various cities using homing pigeons.
[10]
In the early 19th century, the Dutch government used the system in Java and Sumatra. And in
1849, Paul Julius Reuter started a pigeon service to fly stock prices between Aachen and Brussels,
a service that operated for a year until the gap in the telegraph link was closed.[11]
In the Middle Ages, chains of beacons were commonly used on hilltops as a means of relaying a
signal. Beacon chains suffered the drawback that they could only pass a single bit of information, so
the meaning of the message such as "the enemy has been sighted" had to be agreed upon in
advance. One notable instance of their use was during the Spanish Armada, when a beacon chain
relayed a signal from Plymouth to London.[12]
In 1792, Claude Chappe, a French engineer, built the first fixed visual telegraphy system
(or semaphore line) between Lille and Paris.[13] However semaphore suffered from the need for
skilled operators and expensive towers at intervals of ten to thirty kilometres (six to nineteen miles).
As a result of competition from the electrical telegraph, the last commercial line was abandoned in
1880.[14]
Telegraph and telephone[edit]
On 25 July 1837 the first commercial electrical telegraph was demonstrated by
English inventor Sir William Fothergill Cooke, and English scientist Sir Charles Wheatstone.[15][16] Both
inventors viewed their device as "an improvement to the [existing] electromagnetic telegraph" not as
a new device.[17]
Samuel Morse independently developed a version of the electrical telegraph that he unsuccessfully
demonstrated on 2 September 1837. His code was an important advance over Wheatstone's
signaling method. The first transatlantic telegraph cable was successfully completed on 27 July
1866, allowing transatlantic telecommunication for the first time.[18]
The conventional telephone was patented by Alexander Bell in 1876. Elisha Gray also filed a caveat
for it in 1876. Gray abandoned his caveat and because he did not contest Bell's priority, the
examiner approved Bell's patent on March 3, 1876. Gray had filed his caveat for the variable
resistance telephone, but Bell was the first to write down the idea and the first to test it in a
telephone.[88][19] Antonio Meucci invented a device that allowed the electrical transmission of voice
over a line nearly thirty years before in 1849, but his device was of little practical value because it
relied on the electrophonic effect requiring users to place the receiver in their mouths to "hear".
[20]
The first commercial telephone services were set-up by the Bell Telephone Company in 1878 and
1879 on both sides of the Atlantic in the cities of New Haven and London.[21][22]
Radio and television[edit]
Starting in 1894, Italian inventor Guglielmo Marconi began developing a wireless communication
using the then newly discovered phenomenon of radio waves, showing by 1901 that they could be
transmitted across the Atlantic Ocean.[23] This was the start of wireless telegraphy by radio. Voice
and music were demonstrated in 1900 and 1906, but had little early success.[citation needed]
Millimetre wave communication was first investigated by Bengali physicist Jagadish Chandra
Bose during 1894–1896, when he reached an extremely high frequency of up to 60 GHz in his
experiments.[24] He also introduced the use of semiconductor junctions to detect radio waves,[25] when
he patented the radio crystal detector in 1901.[26][27]
World War I accelerated the development of radio for military communications. After the war,
commercial radio AM broadcasting began in the 1920s and became an important mass medium for
entertainment and news. World War II again accelerated development of radio for the wartime
purposes of aircraft and land communication, radio navigation and radar.[28] Development of
stereo FM broadcasting of radio took place from the 1930s on-wards in the United States and
displaced AM as the dominant commercial standard by the 1960s, and by the 1970s in the United
Kingdom.[29]
On 25 March 1925, John Logie Baird was able to demonstrate the transmission of moving pictures
at the London department store Selfridges. Baird's device relied upon the Nipkow disk and thus
became known as the mechanical television. It formed the basis of experimental broadcasts done by
the British Broadcasting Corporation beginning 30 September 1929.[30] However, for most of the
twentieth century televisions depended upon the cathode ray tube invented by Karl Braun. The first
version of such a television to show promise was produced by Philo Farnsworth and demonstrated
to his family on 7 September 1927.[31] After World War II, the experiments in television that had been
interrupted were resumed, and it also became an important home entertainment broadcast medium.
