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Telecommunication is the transmission of information by various types of technologies over
wire A wire is a single usually cylindrical, flexible strand or rod of metal. Wires are used to bear mechanical loads or electricity Electricity is the set of physical phenomena associated with the presence and motion Image:Leaving Yong ...

wire
, radio,
optical Optics is the branch of physics Physics (from grc, φυσική (ἐπιστήμη), physikḗ (epistḗmē), knowledge of nature, from ''phýsis'' 'nature'), , is the natural science that studies matter, its Motion (physics), motion a ...

optical
, or other
electromagnetic Electromagnetism is a branch of physics involving the study of the electromagnetic force, a type of physical interaction that occurs between electric charge, electrically charged particles. The electromagnetic force is carried by electromagneti ...

electromagnetic
systems. It has its origin in the desire of humans for communication over a distance greater than that feasible with the
human voice The human voice consists of sound made by a human being using the vocal tract, including Speech, talking, singing, Laughter, laughing, crying, screaming, shouting, or yelling. The human voice frequency is specifically a part of human sound pro ...
, but with a similar scale of expediency; thus, slow systems (such as
postal mail The mail or post is a system for physically transporting postcard A postcard or post card is a piece of thick paper or thin cardboard, typically rectangular, intended for writing and mailing without an envelope. Non-rectangular shapes may ...
) are excluded from the field. The
transmission media A transmission medium is something that can mediate the propagation of signal In signal processing Signal processing is an electrical engineering subfield that focuses on analysing, modifying, and synthesizing signals such as audio sign ...
in telecommunication have evolved through numerous stages of technology, from
beacon A beacon is an intentionally conspicuous device designed to attract attention to a specific location. A common example is the lighthouse A lighthouse is a tower, building, or another type of structure designed to emit light from a system of lam ...
s and other visual signals (such as
smoke signal The smoke signal is one of the oldest forms of long-distance communication. It is a form of visual communication used over a long distance. In general smoke signals are used to transmit news, signal danger, or to gather people to a common area. ...
s, semaphore telegraphs,
signal flag Flag signals can mean any of various methods of using flags or pennants to send signals. Flags may have individual significance as signals, or two or more flags may be manipulated so that their relative positions convey symbols. Flag signals allow ...
s, and optical
heliograph A heliograph ('' helios'' (), meaning "sun", and '' graphein'' (), meaning "write") is a semaphore system that signals by flashes of sunlight (generally using Morse code) reflected by a mirror. The flashes are produced by momentarily pivoting ...

heliograph
s), to
electrical cable An electrical cable is an assembly of one or more wires running side by side or bundled, which is used to carry electric current. A cable assembly is the composition of one or more electrical cables and their corresponding electrical connectors ...
and
electromagnetic radiation In physics Physics is the natural science that studies matter, its Elementary particle, fundamental constituents, its Motion (physics), motion and behavior through Spacetime, space and time, and the related entities of energy and force. ...
, including light. Such transmission paths are often divided into
communication channel Image:Communications men.jpg, 220px, Old telephone wires are a challenging communications channel for modern digital communications. A communication channel refers either to a physical transmission medium such as a wire, or to a connection-oriented ...
s, which afford the advantages of
multiplexing In telecommunications Telecommunication is the transmission of information by various types of technologies over wire, radio, Optical system, optical, or other Electromagnetism, electromagnetic systems. It has its origin in the desire of ...
multiple concurrent
communication session In computer science Computer science deals with the theoretical foundations of information, algorithms and the architectures of its computation as well as practical techniques for their application. Computer science is the study of Algorit ...
s. ''Telecommunication'' is often used in its plural form. Other examples of pre-modern long-distance communication included audio messages, such as coded drumbeats, lung-blown
hornsHorns or The Horns may refer to: * The Horns (Colorado), a summit on Cheyenne Mountain * ''Horns'' (novel), a dark fantasy novel written in 2010 by Joe Hill ** ''Horns'' (film), a 2013 film adaptation of Hill's novel * "The Horns" (song), a 2015 ...

horns
, and loud
whistle A whistle is an instrument which produces sound from a stream of gas, most commonly air. It may be mouth-operated, or powered by air pressure, steam, or other means. Whistles vary in size from a small slide whistle or nose flute type to a large m ...

whistle
s. 20th- and 21st-century technologies for long-distance communication usually involve electrical and electromagnetic technologies, such as
telegraph Telegraphy is the long-distance transmission of textual messages where the sender uses a semaphore system, known to the recipient, rather than a physical exchange of an object bearing the message. Thus flag semaphore Flag semaphore (from ...
, telephone, television and
teleprinter A teleprinter (teletypewriter, teletype or TTY) is an electromechanical device that can be used to send and receive typed messages through various communications channels, in both point-to-point and point-to-multipoint In telecommunicatio ...
,
networks Network and networking may refer to: Arts, entertainment, and media * Network (1976 film), ''Network'' (1976 film), a 1976 American film * Network (2019 film), ''Network'' (2019 film), an Indian film * Network (album), ''Network'' (album), a 2004 ...
, radio,
microwave transmission Microwave transmission is the transmission of information by microwave radio waves. Although an experimental microwave telecommunication link across the English Channel was demonstrated in 1931, the development of radar in World War II ...
,
optical fiber An optical fiber (or fibre in British English British English (BrE) is the standard dialect of the English language English is a West Germanic languages, West Germanic language first spoken in History of Anglo-Saxon England, ea ...
, and
communications satellite A communications satellite is an artificial satellite that relays and amplifies radio telecommunication signals via a Transponder (satellite communications), transponder; it creates a communication channel between a source transmitter and a Radio ...
s. A revolution in
wireless communication Wireless communication (or just wireless, when the context allows) is the transfer of information between two or more points that do not use an electrical conductor In physics Physics (from grc, φυσική (ἐπιστήμη), ph ...
began in the first decade of the 20th century with the pioneering developments in
radio communications Radio is the technology of signaling and communicating using radio wave Radio waves are a type of electromagnetic radiation with wavelengths in the electromagnetic spectrum longer than infrared light. Radio waves have frequencies as hig ...
by
Guglielmo Marconi Guglielmo Giovanni Maria Marconi, 1st Marquis of Marconi (; 25 April 187420 July 1937) was an Italian inventor and electrical engineer, known for his pioneering work on long-distance radio transmission, development of Marconi's law, and a ...

Guglielmo Marconi
, who won the
Nobel Prize in Physics ) , image = Nobel Prize.png , alt = A golden medallion with an embossed image of a bearded man facing left in profile. To the left of the man is the text "ALFR•" then "NOBEL", and on the right, the text (smaller) "NAT•" then "M ...
in 1909, and other notable pioneering inventors and developers in the field of electrical and electronic telecommunications. These included
Charles Wheatstone Sir Charles Wheatstone FRS FRSE DCL LLD (6 February 1802 – 19 October 1875), was an English scientist and inventor of many scientific breakthroughs of the Victorian era In the history of the United Kingdom, the Victorian era was ...
and
Samuel Morse Samuel Finley Breese Morse (April 27, 1791 – April 2, 1872) was an American inventor and painter. After having established his reputation as a portrait painter, in his middle age Morse contributed to the invention of a single-wire telegraph ...
(inventors of the telegraph),
Antonio Meucci
Antonio Meucci
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 inventing and patenting the first practical telephone A telephone is a tele ...

Alexander Graham Bell
(some of the inventors and developers of the telephone, see
Invention of the telephone The invention of the telephone was the culmination of work done by many individuals, and led to an array of lawsuits relating to the patent claims of several individuals and numerous companies. Early development The concept of the telephon ...
),
Edwin Armstrong Edwin Howard Armstrong (December 18, 1890 – February 1, 1954) was an American electrical engineer and inventor, who developed FM (frequency modulation) radio and the superheterodyne receiver system. He held 42 patents and received numerous award ...
and
Lee de Forest Lee de Forest (August 26, 1873 – June 30, 1961) was an American inventor and early pioneer in radio and in the development of sound-on-film recording used for motion pictures. He had over 180 patents, but also a tumultuous career—he boasted th ...
(inventors of radio), as well as Vladimir K. Zworykin,
John Logie Baird John Logie Baird FRSE Fellowship of the Royal Society of Edinburgh (FRSE) is an award granted to individuals that the Royal Society of Edinburgh, Scotland's national academy of science and Literature, letters, judged to be "eminently disti ...
and
Philo Farnsworth Philo Taylor Farnsworth (August 19, 1906 – March 11, 1971) was an American inventor and television Television (TV), sometimes shortened to tele or telly, is a telecommunication medium used for transmitting moving images in monochrom ...
(some of the inventors of television). According to ''Article 1.3'' of the Radio Regulations (RR), telecommunication is defined as ''« Any
transmission Transmission may refer to: Science and technology * Power transmissionPower transmission is the movement of energy from its place of generation to a location where it is applied to perform useful Mechanical work, work. Power (physics), Power is d ...
, emission or reception of signs, signals, writings, images and sounds or intelligence of any nature by
wire A wire is a single usually cylindrical, flexible strand or rod of metal. Wires are used to bear mechanical loads or electricity Electricity is the set of physical phenomena associated with the presence and motion Image:Leaving Yong ...

wire
, radio, optical, or other
electromagnetic Electromagnetism is a branch of physics involving the study of the electromagnetic force, a type of physical interaction that occurs between electric charge, electrically charged particles. The electromagnetic force is carried by electromagneti ...
systems''.» This definition is identical to those contained in the Annex to the
Constitution and Convention of the International Telecommunication Union The Constitution and Convention of the International Telecommunication Union (short: ITU Constitution and Convention  | also: CS CV) is an international treaty, signed and ratification, ratified by almost all countries of the world. The t ...
(Geneva, 1992). The early telecommunication networks were created with copper wires as the physical medium for signal transmission. For many years, these networks were used for basic phone services, namely voice and telegrams. Since the mid-1990s, as the internet has grown in popularity, voice has been gradually supplanted by data. This soon demonstrated the limitations of copper in data transmission, prompting the development of optics.


Etymology

The word ''telecommunication'' is a compound of the Greek prefix ''tele'' (τῆλε), meaning ''distant'', ''far off'', or ''afar'', and the Latin ''communicare'', meaning ''to share''. Its modern use is adapted from the French, because its written use was recorded in 1904 by the French engineer and novelist Édouard Estaunié. ''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".


History


Beacons and pigeons

Homing pigeon The true messenger pigeon is a variety of domestic pigeons (''Columba livia domestica'') derived from the wild rock dove, selectively bred for its ability to find its way home over extremely long distances. The rock dove has an innate homing ab ...

Homing pigeon
s have occasionally been used throughout history by different cultures.
Pigeon post Pigeon post is the use of homing pigeons to carry messages. Pigeons are effective as messengers due to their natural homing abilities. The pigeons are transported to a destination in cages, where they are attached with messages, then the pigeon ...

Pigeon post
had
Persia Iran ( fa, ایران ), also called Persia, and officially the Islamic Republic of Iran, is a country in Western Asia Western Asia, also West Asia, is the westernmost subregion of Asia. It is entirely a part of the Greater Middle Ea ...

Persia
n roots, and was later used by the Romans to aid their military.
Frontinus Sextus Julius Frontinus (c. 40 – 103 AD) was a prominent Roman Empire, Roman civil engineer, author, soldier and senator of the late 1st century AD. He was a successful general under Domitian, commanding forces in Roman Britain, and on the Rhin ...
said that
Julius Caesar Gaius Julius Caesar (; 12 July 100 BC – 15 March 44 BC) was a Roman Roman or Romans usually refers to: *Rome, the capital city of Italy *Ancient Rome, Roman civilization from 8th century BC to 5th century AD *Roman people, the people of anc ...

Julius Caesar
used pigeons as messengers in his conquest of
Gaul Gaul ( la, Gallia) was a region of Western Europe Western Europe is the region of Europe Europe is a continent A continent is one of several large landmasses. Generally identified by convention (norm), convention rather than a ...

Gaul
. The
Greeks The Greeks or Hellenes (; el, Έλληνες, ''Éllines'' ) are an ethnic group and nation native to the Eastern Mediterranean and the Black Sea regions, namely Greece, Greek Cypriots, Cyprus, Greeks in Albania, Albania, Greeks in Italy, Ital ...

Greeks
also conveyed the names of the victors at the
Olympic Games The modern Olympic Games or Olympics (french: Jeux olympiques) are leading international sporting events featuring summer and winter sports competitions in which thousands of athletes from around the world participate in a multi-sport event, ...
to various cities using homing pigeons. In the early 19th century, the Dutch government used the system in
Java Java ( id, Jawa, ; jv, ꦗꦮ; su, ) is one of the islands of the Greater Sunda Islands in Indonesia Indonesia ( ), officially the Republic of Indonesia ( id, Republik Indonesia, links=yes ), is a country in Southeast Asia and Oceania ...
and
Sumatra Sumatra is one of the Sunda Islands of western Indonesia. It is the largest island that is fully within Indonesian territory, as well as the list of islands by area, sixth-largest island in the world at 473,481 km2 (182,812 mi.2), not ...

Sumatra
. And in 1849,
Paul Julius Reuter Paul Julius Reuter (born Israel Beer Josaphat; 21 July 1816 – 25 February 1899), later titled as Freiherr von Reuter (Baron von Reuter), was a German-born British entrepreneur who was a pioneer of telegraphy Telegraphy is the long-dist ...
started a pigeon service to fly stock prices between
Aachen Aachen ( ; Aachen dialect Aachen dialect (natively ''Öcher Platt'') is a dialect of Ripuarian Franconian spoken in the German Rhineland city of Aachen Aachen ( ; Aachen dialect: ''Oche'' ; French and traditional English: Aix-la-Chap ...

Aachen
and
Brussels Brussels (french: Bruxelles or ; nl, Brussel ), officially the Brussels-Capital Region (All text and all but one graphic show the English name as Brussels-Capital Region.) (french: link=no, Région de Bruxelles-Capitale; nl, link=no, Brussel ...
, a service that operated for a year until the gap in the telegraph link was closed. In the Middle Ages, chains of
beacon A beacon is an intentionally conspicuous device designed to attract attention to a specific location. A common example is the lighthouse A lighthouse is a tower, building, or another type of structure designed to emit light from a system of lam ...
s 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 The Spanish Armada ( es, Grande y Felicísima Armada, links=no, lit=Great and Most Fortunate Navy) was a Habsburg Spain, Habsburg Spanish fleet of 130 ships that sailed from Lisbon in late May 1588 under the command of the Alonso Pérez de Guzm ...

Spanish Armada
, when a beacon chain relayed a signal from
Plymouth Plymouth () is a port city A city is a large human settlement.Goodall, B. (1987) ''The Penguin Dictionary of Human Geography''. London: Penguin.Kuper, A. and Kuper, J., eds (1996) ''The Social Science Encyclopedia''. 2nd edition. London: Rou ...

Plymouth
to
London London is the capital city, capital and List of urban areas in the United Kingdom, largest city of England and the United Kingdom. The city stands on the River Thames in the south-east of England, at the head of its estuary leading to the Nor ...

London
. In 1792,
Claude Chappe Claude Chappe (25 December 1763 – 23 January 1805) was a French inventor who in 1792 demonstrated a practical semaphore system that eventually spanned all of France. His system consisted of a series of towers, each within line of sight of ot ...
, a French engineer, built the first fixed visual
telegraphy 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 Flag semaphore (from the Greek σ ...
system (or
semaphore line An optical telegraph is a semaphore Semaphore is the use of an apparatus with telegraphy Telegraphy is the long-distance transmission of textual messages where the sender uses a semaphore system, known to the recipient, rather than ...
) between
Lille Lille ( , ; nl, Rijsel ; pcd, Lile; vls, Rysel) is a city at the northern part of France France (), officially the French Republic (french: link=no, République française), is a country primarily located in Western Europe, consisting ...

Lille
and Paris. 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.


Telegraph and telephone

On 25 July 1837 the first commercial
electrical telegraph An electrical telegraph was a point-to-point text messaging system, used from the 1840s until the mid 20th century when it was slowly replaced by other telecommunication systems. At the sending station switches connected a source of current to ...
was demonstrated by English inventor Sir
William Fothergill Cooke Sir William Fothergill Cooke (4 May 1806 – 25 June 1879) was an English inventor. He was, with Charles Wheatstone, the co-inventor of the Cooke and Wheatstone telegraph, Cooke-Wheatstone electrical telegraph, which was patented in May 1837. Tog ...
, and English scientist Sir
Charles Wheatstone Sir Charles Wheatstone FRS FRSE DCL LLD (6 February 1802 – 19 October 1875), was an English scientist and inventor of many scientific breakthroughs of the Victorian era In the history of the United Kingdom, the Victorian era was ...
. Both inventors viewed their device as "an improvement to the xistingelectromagnetic telegraph" not as a new device.
Samuel Morse Samuel Finley Breese Morse (April 27, 1791 – April 2, 1872) was an American inventor and painter. After having established his reputation as a portrait painter, in his middle age Morse contributed to the invention of a single-wire telegraph ...

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 Transatlantic telegraph cables were Submarine communications cable, undersea cables running under the Atlantic Ocean used for telegraph communications. Telegraphy is now an obsolete form of communication and the cables have long since been decomm ...
was successfully completed on 27 July 1866, allowing transatlantic telecommunication for the first time. The conventional telephone was patented by
Alexander Bell
Alexander Bell
in 1876.
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, deve ...

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 3 March 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. 8
Antonio Meucci
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". 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 New Haven is a coastal city in the U.S. state of Connecticut. It is located on New Haven Harbor on the northern shore of Long Island Sound in New Haven County, Connecticut, and is part of the New York metropolitan area. With a population of ...
and London.


Radio and television

Starting in 1894, Italian inventor
Guglielmo Marconi Guglielmo Giovanni Maria Marconi, 1st Marquis of Marconi (; 25 April 187420 July 1937) was an Italian inventor and electrical engineer, known for his pioneering work on long-distance radio transmission, development of Marconi's law, and a ...

Guglielmo Marconi
began developing a wireless communication using the then newly discovered phenomenon of
radio wave Radio waves are a type of electromagnetic radiation In physics Physics (from grc, φυσική (ἐπιστήμη), physikḗ (epistḗmē), knowledge of nature, from ''phýsis'' 'nature'), , is the natural science that studies ma ...
s, showing by 1901 that they could be transmitted across the Atlantic Ocean. This was the start of
wireless telegraphy Wireless telegraphy or radiotelegraphy is transmission of telegraph Telegraphy is the long-distance transmission of textual messages where the sender uses a semaphore system, known to the recipient, rather than a physical exchange of an ...
by radio. On 17 December 1902, a transmission from the Marconi station in
Glace Bay Glace Bay ( Scottish Gaelic: ''Glasbaidh'') is a community in the eastern part of the Cape Breton Regional Municipality in Nova Scotia, Canada. It forms part of the general area referred to as Industrial Cape Breton. Formerly an incorporated ...

Glace Bay
, Nova Scotia, Canada, became the world's first radio message to cross the Atlantic from North America and in 1904 a commercial service was established to transmit nightly news summaries to subscribing ships, which could incorporate them into their on-board newspapers.
Millimetre wave The millimetre ( international spelling; SI unit symbol mm) or millimeter ( American spelling) is a unit Unit may refer to: Arts and entertainment * UNIT, a fictional military organization in the science fiction television series ''Doctor Who'' ...
communication was first investigated by
Bengali Bengali or Bengalee, or Bengalese may refer to: *something of, from, or related to Bengal, a large region in South Asia * Bengalis, an ethnic and linguistic group of the region * Bengali language, the language they speak ** Bengali alphabet, the wr ...
physicist
Jagadish Chandra Bose Sir Jagadish Chandra Bose (;, ; 30 November 1858 – 23 November 1937) was a Bengali polymath, biologist, physicist A physicist is a scientist A scientist is a person who conducts Scientific method, scientific research to advance knowl ...

Jagadish Chandra Bose
during 18941896, when he reached an
extremely high frequency Extremely high frequency (EHF) is the International Telecommunication Union File:ITU monument, Bern.jpg, 260px, ITU Monument, Bern The International Telecommunication Union is a list of specialized agencies of the United Nations, specializ ...
of up to 60
GHz The hertz (symbol: Hz) is the derived unit of frequency Frequency is the number of occurrences of a repeating event per unit of time. It is also referred to as temporal frequency, which emphasizes the contrast to spatial frequency and an ...
in his experiments. He also introduced the use of
semiconductor A semiconductor material has an electrical conductivity Electrical resistivity (also called specific electrical resistance or volume resistivity) is a fundamental property of a material that quantifies how strongly it resists electric curre ...
junctions to detect radio waves, reprinted in Igor Grigorov, Ed.,
Antentop
'', Vol. 2, No.3, pp. 87–96.
when he
patented NPOV disputes from March 2021 A patent is a title A title is one or more words used before or after a person's name, in certain contexts. It may signify either generation, an official position, or a professional or academic qualification. In ...
the radio
crystal detector A crystal detector is an electronic component An electronic component is any basic discrete device or physical entity in an electronic system used to affect electrons or their associated fields. Electronic components are mostly industrial ...
in 1901.
World War I World War I or the First World War, often abbreviated as WWI or WW1, was a global war originating in Europe that lasted from 28 July 1914 to 11 November 1918. Contemporaneously known as the Great War or "The war to end war, the war ...

World War I
accelerated the development of radio for
military communications Military communications or military signals involve all aspects of communication Communication (from Latin ''communicare'', meaning "to share" or "to be in relation with") is "an apparent answer to the painful divisions between self and othe ...
. After the war, commercial radio
AM broadcasting AM broadcasting is radio broadcasting using amplitude modulation (AM) transmissions. It was the first method developed for making audio radio transmissions, and is still used worldwide, primarily for medium wave (also known as "AM band") transmiss ...
began in the 1920s and became an important mass medium for entertainment and news.
World War II World War II or the Second World War, often abbreviated as WWII or WW2, was a World war, global war that lasted from 1939 to 1945. It involved World War II by country, the vast majority of the world's countries—including all the great ...
again accelerated the development of radio for the wartime purposes of aircraft and land communication, radio navigation and radar. Development of stereo
FM broadcasting in Henderson, Nevada Henderson is a city in Clark County, Nevada Nevada (, ) is a U.S. state, state in the Western United States, Western region of the United States. It is bordered by Oregon to the northwest, Idaho to the northeast, Calif ...
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. On 25 March 1925,
John Logie Baird John Logie Baird FRSE Fellowship of the Royal Society of Edinburgh (FRSE) is an award granted to individuals that the Royal Society of Edinburgh, Scotland's national academy of science and Literature, letters, judged to be "eminently disti ...
was able to demonstrate the transmission of moving pictures at the London department store
Selfridges Selfridges, also known as Selfridges & Co., is a chain of high-end department stores in the United Kingdom that is operated by Canadian group Selfridges Retail Limited, part of the Selfridges Group of department stores. It was founded by Harry G ...

Selfridges
. Baird's device relied upon the
Nipkow disk 300px, Schematic showing the circular paths traced by the holes in a Nipkow disk A Nipkow disk (sometimes Anglicized as Nipkov disk; patented in 1884), also known as scanning disk, is a mechanical, rotating, geometrically operating image scanning ...

Nipkow disk
and thus became known as the
mechanical television Mechanical television or mechanical scan television is a television Television (TV), sometimes shortened to tele or telly, is a telecommunication medium used for transmitting moving images in monochrome (black and white), or in color, a ...
. It formed the basis of experimental broadcasts done by the
British Broadcasting Corporation The British Broadcasting Corporation (BBC) is a public service broadcaster, headquartered at Broadcasting House Broadcasting House is the headquarters of the BBC, in Portland Place and Langham Place, London A map showing the Langha ...
beginning 30 September 1929. However, for most of the twentieth-century televisions depended upon the
cathode ray tube File:CRT monochrome.png, 250px, Cutaway rendering of a monochrome CRT: 1. Deflection coils2. Electron beam3. Focusing coil4. Phosphor layer on the inner side of the screen; emits light when struck by the electron beam5.&nbs ...

cathode ray tube
invented by Karl Braun. The first version of such a television to show promise was produced by
Philo Farnsworth Philo Taylor Farnsworth (August 19, 1906 – March 11, 1971) was an American inventor and television Television (TV), sometimes shortened to tele or telly, is a telecommunication medium used for transmitting moving images in monochrom ...
and demonstrated to his family on 7 September 1927. After
World War II World War II or the Second World War, often abbreviated as WWII or WW2, was a World war, global war that lasted from 1939 to 1945. It involved World War II by country, the vast majority of the world's countries—including all the great ...
, the experiments in television that had been interrupted were resumed, and it also became an important home entertainment broadcast medium.


Thermionic valves

The type of device known as a '' thermionic tube'' or ''thermionic valve'' uses the phenomenon of
thermionic emission One of the bulbs with which Edison discovered thermionic emission. It consists of an evacuated glass light bulb containing a filament The word filament, which is descended from Latin ''filum'' meaning " thread", is used in English for a variety o ...
of electrons from a heated
cathode A cathode is the electrode from which a conventional current leaves a polarized electrical device. This definition can be recalled by using the mnemonic ''CCD'' for ''Cathode Current Departs''. A conventional current describes the direction in which ...

cathode
and is used for a number of fundamental electronic functions such as signal amplification and current
rectification Rectification has the following technical meanings: Mathematics * Rectification (geometry), truncating a polytope by marking the midpoints of all its edges, and cutting off its vertices at those points * Rectifiable curve, in mathematics * Rectif ...

rectification
. Non-thermionic types, such as a vacuum
phototube A phototube or photoelectric cell is a type of gas-filled or vacuum tube A vacuum tube, an electron tube, valve (British usage) or tube (North America), is a device that controls electric current flow in a high vacuum between electrodes to whi ...
however, achieve electron emission through the
photoelectric effect The photoelectric effect is the emission of electrons when electromagnetic radiation, such as light, hits a material. Electrons emitted in this manner are called photoelectrons. The phenomenon is studied in condensed matter physics, and Solid-state ...

photoelectric effect
, and are used for such as the detection of light levels. In both types, the electrons are accelerated from the cathode to the
anode An anode is an electrode An electrode is an electrical conductor used to make contact with a nonmetallic part of a circuit (e.g. a semiconductor A semiconductor material has an Electrical resistivity and conductivity, electrical conductivit ...
by the
electric field An electric field (sometimes E-field) is the physical field that surrounds electrically-charged particle In physics Physics (from grc, φυσική (ἐπιστήμη), physikḗ (epistḗmē), knowledge of nature, from ''phýsis'' ' ...
in the tube. The simplest vacuum tube, the
diode Various semiconductor diodes. Bottom: A bridge rectifier. In most diodes, a white or black painted band identifies the cathode into which electrons will flow when the diode is conducting. Electron flow is the reverse of conventional current flow ...
invented in 1904 by
John Ambrose Fleming Sir John Ambrose Fleming FRS (29 November 1849 – 18 April 1945) was an English electrical engineer and physicist who invented the first thermionic valve or vacuum tube A vacuum tube, an electron tube, valve (British usage) or tube ( ...
, contains only a heated electron-emitting cathode and an anode. Electrons can only flow in one direction through the device—from the cathode to the anode. Adding one or more
control grid The control grid is an electrode An electrode is an electrical conductor used to make contact with a nonmetallic part of a circuit (e.g. a semiconductor A semiconductor material has an Electrical resistivity and conductivity, electrical cond ...
s within the tube allows the current between the cathode and anode to be controlled by the voltage on the grid or grids. These devices became a key component of electronic circuits for the first half of the twentieth century. They were crucial to the development of radio, television, radar,
sound recording and reproduction Sound recording and reproduction is an electrical Electricity is the set of physical phenomena associated with the presence and motion Image:Leaving Yongsan Station.jpg, 300px, Motion involves a change in position In physics, motion ...
, long-distance telephone networks, and analogue and early digital
computers A computer is a machine that can be programmed to Execution (computing), carry out sequences of arithmetic or logical operations automatically. Modern computers can perform generic sets of operations known as Computer program, programs. These p ...
. Although some applications had used earlier technologies such as the
spark gap transmitter A spark-gap transmitter is an obsolete type of transmitter, radio transmitter which generates radio waves by means of an electric spark."Radio Transmitters, Early" in Spark-gap transmitters were the first type of radio transmitter, and were the ma ...

spark gap transmitter
for radio or
mechanical computer A mechanical computer is built from mechanical components such as lever A lever ( or ) is a simple machine consisting of a beam (structure), beam or rigid rod pivoted at a fixed hinge, or '':wikt:fulcrum, fulcrum''. A lever is a rigid body capa ...
s for computing, it was the invention of the thermionic vacuum tube that made these technologies widespread and practical, and created the discipline of
electronics Electronics comprises the physics, engineering, technology and applications that deal with the emission, flow and control of electrons in vacuum and matter. It uses active devices to control electron flow by amplifier, amplification and rectifie ...
. In the 1940s the invention of
semiconductor devices A semiconductor A semiconductor material has an Electrical resistivity and conductivity, electrical conductivity value falling between that of a Electrical conductor, conductor, such as metallic copper, and an insulator (electricity), insulato ...
made it possible to produce solid-state devices, which are smaller, more efficient, reliable and durable, and cheaper than thermionic tubes. From the mid-1960s, thermionic tubes were then being replaced with the
transistor file:MOSFET Structure.png, upright=1.4, Metal-oxide-semiconductor field-effect transistor (MOSFET), showing Metal gate, gate (G), body (B), source (S) and drain (D) terminals. The gate is separated from the body by an insulating layer (pink). A ...

transistor
. Thermionic tubes still have some applications for certain high-frequency amplifiers.


Semiconductor era

The modern period of telecommunication history from 1950 onwards is referred to as the
semiconductor A semiconductor material has an electrical conductivity Electrical resistivity (also called specific electrical resistance or volume resistivity) is a fundamental property of a material that quantifies how strongly it resists electric curre ...
era, due to the wide adoption of
semiconductor devices A semiconductor A semiconductor material has an Electrical resistivity and conductivity, electrical conductivity value falling between that of a Electrical conductor, conductor, such as metallic copper, and an insulator (electricity), insulato ...
in telecommunication technology. The development of
transistor file:MOSFET Structure.png, upright=1.4, Metal-oxide-semiconductor field-effect transistor (MOSFET), showing Metal gate, gate (G), body (B), source (S) and drain (D) terminals. The gate is separated from the body by an insulating layer (pink). A ...

transistor
technology and the
semiconductor industry The semiconductor industry is the aggregate of companies engaged in the design and fabrication of semiconductor A semiconductor material has an Electrical resistivity and conductivity, electrical conductivity value falling between that of a ...
enabled significant advances in telecommunication technology, and led to a transition away from state-owned
narrowband {{refimprove, date=March 2011 In radio communications, a narrowband channel is a channel in which the bandwidth of the message does not significantly exceed the channel's coherence bandwidth. In the study of wired channels, ''narrowband'' impli ...
circuit-switched networks to private broadband
packet-switched network In telecommunication Telecommunication is the transmission of information Information can be thought of as the resolution of uncertainty; it answers the question of "What an entity is" and thus defines both its essence and the nature of ...
s.
Metal–oxide–semiconductor The metal–oxide–semiconductor field-effect transistor (MOSFET, MOS-FET, or MOS FET), also known as the metal–oxide–silicon transistor (MOS transistor, or MOS), is a type of insulated-gate field-effect transistor The field-effect trans ...
(MOS) technologies such as
large-scale integration An integrated circuit or monolithic integrated circuit (also referred to as an IC, a chip, or a microchip) is a set of electronic circuit File:PExdcr01CJC.jpg, 200px, A circuit built on a printed circuit board (PCB). An electronic circuit i ...
(LSI) and RF CMOS (
radio-frequency Radio frequency (RF) is the oscillation rate of an alternating electric current or voltage or of a magnetic, electric or electromagnetic field or mechanical system in the frequency range from around to around . This is roughly between the ...
complementary MOS), along with
information theory Information theory is the scientific study of the quantification (science), quantification, computer data storage, storage, and telecommunication, communication of Digital data, digital information. The field was fundamentally established by the ...
(such as
data compression In signal processing Signal processing is an electrical engineering subfield that focuses on analysing, modifying, and synthesizing signals such as audio signal processing, sound, image processing, images, and scientific measurements. Signal ...
), led to a transition from analog to
digital signal processing#REDIRECT Digital signal processing {{Redirect category shell, 1= {{R from other capitalisation ...
, with the introduction of digital telecommunications (such as
digital telephony Telephony ( ) is the field of technology involving the development, application, and deployment of telecommunication Telecommunication is the transmission of information Information can be thought of as the resolution of uncertainty; it ...
and
digital media Digital media means any communication media that operate with the use of any of various encoded machine-readable data Machine-readable data, or computer-readable data, is data Data are units of information Information can be thought ...
) and
wireless communications Wireless communication (or just wireless, when the context allows) is the transfer of information between two or more points that do not use an electrical conductor In physics Physics (from grc, φυσική (ἐπιστήμη), ph ...
(such as
cellular networks A cellular network or mobile network is a communication network where the last link is wireless Wireless communication (or just wireless, when the context allows) is the transfer of information between two or more points that do not use an ...
and
mobile telephony Mobile telephony is the provision of telephone services to phones which may move around freely rather than stay fixed in one location. Telephony is supposed to specifically point to a voice-only service or connection, though sometimes the li ...
), leading to rapid growth of the
telecommunications industryThe telecommunications industries within the sector of information and communication technology Information can be thought of as the resolution of uncertainty Uncertainty refers to Epistemology, epistemic situations involving imperfect or ...
towards the end of the 20th century.


Transistors

The development of
transistor file:MOSFET Structure.png, upright=1.4, Metal-oxide-semiconductor field-effect transistor (MOSFET), showing Metal gate, gate (G), body (B), source (S) and drain (D) terminals. The gate is separated from the body by an insulating layer (pink). A ...

transistor
technology has been fundamental to modern
electronic Electronic may refer to: *Electronics Electronics comprises the physics, engineering, technology and applications that deal with the emission, flow and control of electrons in vacuum and matter. It uses active devices to control electron flow b ...
telecommunication. The first transistor, a
point-contact transistor The point-contact transistor was the first type of transistor to be successfully demonstrated. It was developed by research scientists John Bardeen and Walter Brattain at Bell Laboratories in December 1947. They worked in a group led by physici ...

point-contact transistor
, was invented by
John Bardeen John Bardeen (; May 23, 1908 – January 30, 1991) was an American engineer Engineers, as practitioners of engineering, are Professional, professionals who Invention, invent, design, analyze, build and test Machine, machines, complex systems, ...
and
Walter Houser Brattain Walter Houser Brattain (; February 10, 1902 – October 13, 1987) was an American physicist at Bell Labs Nokia Bell Labs (formerly named Bell Labs Innovations (1996–2007), AT&T Bell Laboratories (1984–1996) and Bell Telephone Laboratories ...
at
Bell Labs Nokia Bell Labs (formerly named Bell Labs Innovations (1996–2007), AT&T Bell Laboratories (1984–1996) and Bell Telephone Laboratories (1925–1984)) is an American industrial Research and development, research and scientific development S.A. ...
in 1947. The
MOSFET The metal–oxide–semiconductor field-effect transistor (MOSFET, MOS-FET, or MOS FET), also known as the metal–oxide–silicon transistor (MOS transistor, or MOS), is a type of insulated-gate field-effect transistor The field-effect trans ...

MOSFET
(metal–oxide–silicon field-effect transistor), also known as the MOS transistor, was later invented by and
Dawon Kahng Dawon Kahng ( ko, 강대원; May 4, 1931 – May 13, 1992) was a Korean-American electrical engineer and inventor, known for his work in solid-state electronics. He is best known for inventing the MOSFET (metal–oxide–semiconductor field-effect ...

Dawon Kahng
at Bell Labs in 1959. The MOSFET is the building block or "workhorse" of the
information revolution The term information revolution describes current economic, social and technological trends beyond the Industrial Revolution The Industrial Revolution was the transition to new manufacturing processes in Europe and the United States, in the p ...
and the
information age The Information Age (also known as the Computer Age, Digital Age, or New Media Age) is a historical periodHuman history is commonly divided into three main Era, eras — Ancient history, Ancient, Post-classical history, Post-classical, and Mode ...
, and the most widely manufactured device in history. MOSFET, MOS technology, including MOS integrated circuits and power MOSFETs, drives the communications infrastructure of modern telecommunication. Along with computers, other essential elements of modern telecommunication that are built from MOSFETs include mobile devices, transceivers, base station modules, Router (computing), routers, RF power amplifiers, microprocessors, memory chips, and telecommunication circuits. According Edholm's law, the bandwidth (signal processing), bandwidth of telecommunication networks has been doubling every 18 months. Advances in MOS technology, including MOSFET scaling (increasing transistor counts at an exponential pace, as predicted by Moore's law), has been the most important contributing factor in the rapid rise of bandwidth in telecommunications networks.


Computer networks and the Internet

On 11 September 1940, George Stibitz transmitted problems for his Complex Number Calculator in New York using a Teleprinter, teletype, and received the computed results back at Dartmouth College in New Hampshire. This configuration of a centralized computer (Mainframe computer, mainframe) with remote dumb terminals remained popular well into the 1970s. However, already in the 1960s, researchers started to investigate packet switching, a technology that sends a message in portions to its destination Asynchronous Transfer Mode, asynchronously without passing it through a centralized mainframe. A four-node (networking), node computer network, network emerged on 5 December 1969, constituting the beginnings of the ARPANET, which by 1981 had grown to 213 nodes. ARPANET eventually merged with other networks to form the Internet. While Internet development was a focus of the Internet Engineering Task Force (IETF) who published a series of Request for Comments documents, other networking advancements occurred in industrial laboratory, industrial laboratories, such as the local area network (LAN) developments of Ethernet (1983) and Token Ring (1984).


Wireless telecommunication

The wireless revolution began in the 1990s, with the advent of digital wireless networks leading to a social revolution, and a paradigm shift from wired to wireless technology, including the proliferation of commercial wireless technologies such as cell phones,
mobile telephony Mobile telephony is the provision of telephone services to phones which may move around freely rather than stay fixed in one location. Telephony is supposed to specifically point to a voice-only service or connection, though sometimes the li ...
, pagers, wireless computer networks, cellular networks, the wireless Internet, and laptop and handheld computers with wireless connections. The wireless revolution has been driven by advances in radio-frequency engineering, radio frequency (RF) and microwave engineering, and the transition from analog to digital RF technology. Advances in metal–oxide–semiconductor field-effect transistor (MOSFET, or MOS transistor) technology, the key component of the RF technology that enables digital wireless networks, has been central to this revolution, including MOS devices such as the power MOSFET, LDMOS, and RF CMOS.


Digital media

Practical
digital media Digital media means any communication media that operate with the use of any of various encoded machine-readable data Machine-readable data, or computer-readable data, is data Data are units of information Information can be thought ...
digital distribution, distribution and streaming media, streaming were made possible by advances in
data compression In signal processing Signal processing is an electrical engineering subfield that focuses on analysing, modifying, and synthesizing signals such as audio signal processing, sound, image processing, images, and scientific measurements. Signal ...
, due to the impractically high memory, storage and bandwidth requirements of uncompressed media. The most important compression technique is the discrete cosine transform (DCT), a lossy compression algorithm that was first proposed as an image compression technique in 1972. Realization and demonstration, on 29 October 2001, of the first digital cinema transmission by communications satellite, satellite in Europe of a feature film by Bernard Pauchon, Alain Lorentz, Raymond Melwig and Philippe Binant.


Growth of transmission capacity

The effective capacity to exchange information worldwide through two-way telecommunication networks grew from 281 petabytes (pB) of optimally compressed information in 1986, to 471 pB in 1993, to 2.2 exabytes (eB) in 2000, and to 65 eB in 2007."The World’s Technological Capacity to Store, Communicate, and Compute Information"
, Martin Hilbert and Priscila López (2011), Science (journal), Science, 332(6025), 60–65; free access to the study through here: martinhilbert.net/WorldInfoCapacity.html
This is the informational equivalent of two newspaper pages per person per day in 1986, and six entire newspapers per person per day by 2007. Given this growth, telecommunications play an increasingly important role in the world economy and the global telecommunications industry was about a US$4.7 trillion sector in 2012.Worldwide Telecommunications Industry Revenues
, Internet Engineering Task Force, June 2010.
Introduction to the Telecommunications Industry
, Internet Engineering Task Force, June 2012.
The service revenue of the global telecommunications industry was estimated to be $1.5 trillion in 2010, corresponding to 2.4% of the world's gross domestic product (GDP).


Technical concepts

Modern telecommunication is founded on a series of key concepts that experienced progressive development and refinement in a period of well over a century.


Basic elements

Telecommunication technologies may primarily be divided into wired and wireless methods. Overall though, a basic communication system, telecommunication system consists of three main parts that are always present in some form or another: * A transmitter that takes information and converts it to a signal (electrical engineering), signal. * A transmission medium, also called the ''physical channel'' that carries the signal. An example of this is the Free-space optical communication, "free space channel". * A receiver (radio), receiver that takes the signal from the channel and converts it back into usable information for the recipient. For example, in a radio station, radio broadcasting station the station's large power amplifier is the transmitter; and the broadcasting antenna (radio), antenna is the interface between the power amplifier and the "free space channel". The free space channel is the transmission medium; and the receiver's antenna is the interface between the free space channel and the receiver. Next, the radio receiver is the destination of the radio signal, and this is where it is converted from electricity to sound for people to listen to. Sometimes, telecommunication systems are duplex (telecommunications), "duplex" (two-way systems) with a single box of
electronics Electronics comprises the physics, engineering, technology and applications that deal with the emission, flow and control of electrons in vacuum and matter. It uses active devices to control electron flow by amplifier, amplification and rectifie ...
working as both the transmitter and a receiver, or a ''transceiver''. For example, a cellular telephone is a transceiver. The transmission electronics and the receiver electronics within a transceiver are actually quite independent of each other. This can be readily explained by the fact that radio transmitters contain power amplifiers that operate with electrical powers measured in watts or kilowatts, but radio receivers deal with radio powers that are measured in the microwatts or nanowatts. Hence, transceivers have to be carefully designed and built to isolate their high-power circuitry and their low-power circuitry from each other, as to not cause interference. Telecommunication over fixed lines is called point-to-point communication because it is between one transmitter and one receiver. Telecommunication through radio broadcasts is called broadcasting, broadcast communication because it is between one powerful transmitter and numerous low-power but sensitive radio receivers. Telecommunications in which multiple transmitters and multiple receivers have been designed to cooperate and to share the same physical channel are called multiplexing, multiplex systems. The sharing of physical channels using multiplexing often gives very large reductions in costs. Multiplexed systems are laid out in telecommunication networks, and the multiplexed signals are switched at nodes through to the correct destination terminal receiver.


Analog versus digital communications

Communications signals can be sent either by analog signals or Digital signal (electronics), digital signals. There are analog communication systems and digital communication systems. For an analog signal, the signal is varied continuously with respect to the information. In a digital signal, the information is encoded as a set of discrete values (for example, a set of ones and zeros). During the propagation and reception, the information contained in analog signals will inevitably be degraded by noise (signal processing), undesirable physical noise. (The output of a transmitter is noise-free for all practical purposes.) Commonly, the noise in a communication system can be expressed as adding or subtracting from the desirable signal in a completely random process, random way. This form of noise is called additive noise, with the understanding that the noise can be negative or positive at different instants of time. Noise that is not additive noise is a much more difficult situation to describe or analyze, and these other kinds of noise will be omitted here. On the other hand, unless the additive noise disturbance exceeds a certain threshold, the information contained in digital signals will remain intact. Their resistance to noise represents a key advantage of digital signals over analog signals.


Communication channels

The term "channel" has two different meanings. In one meaning, a channel is the physical medium that carries a signal between the transmitter and the receiver. Examples of this include the atmosphere for sound communications, glass optical fibers for some kinds of optical communications, coaxial cables for communications by way of the voltages and electric currents in them, and Free-space optical communication, free space for communications using visible light, infrared waves, ultraviolet light, and
radio wave Radio waves are a type of electromagnetic radiation In physics Physics (from grc, φυσική (ἐπιστήμη), physikḗ (epistḗmē), knowledge of nature, from ''phýsis'' 'nature'), , is the natural science that studies ma ...
s. Coaxial cable types are classified by RG type or "radio guide", terminology derived from World War II. The various RG designations are used to classify the specific signal transmission applications. This last channel is called the "free space channel". The sending of radio waves from one place to another has nothing to do with the presence or absence of an atmosphere between the two. Radio waves travel through a perfect vacuum just as easily as they travel through air, fog, clouds, or any other kind of gas. The other meaning of the term "channel" in telecommunications is seen in the phrase channel (communications), communications channel, which is a subdivision of a transmission medium so that it can be used to send multiple streams of information simultaneously. For example, one radio station can broadcast radio waves into free space at frequencies in the neighborhood of 94.5 MHz (megahertz) while another radio station can simultaneously broadcast radio waves at frequencies in the neighborhood of 96.1 MHz. Each radio station would transmit radio waves over a frequency bandwidth (signal processing), bandwidth of about 180 kHz (kilohertz), centered at frequencies such as the above, which are called the Carrier wave, "carrier frequencies". Each station in this example is separated from its adjacent stations by 200 kHz, and the difference between 200 kHz and 180 kHz (20 kHz) is an engineering allowance for the imperfections in the communication system. In the example above, the "free space channel" has been divided into communications channels according to frequency, frequencies, and each channel is assigned a separate frequency bandwidth in which to broadcast radio waves. This system of dividing the medium into channels according to frequency is called "frequency-division multiplexing". Another term for the same concept is "wavelength-division multiplexing", which is more commonly used in optical communications when multiple transmitters share the same physical medium. Another way of dividing a communications medium into channels is to allocate each sender a recurring segment of time (a "time slot", for example, 20 milliseconds out of each second), and to allow each sender to send messages only within its own time slot. This method of dividing the medium into communication channels is called "time-division multiplexing" (TDM), and is used in optical fiber communication. Some radio communication systems use TDM within an allocated FDM channel. Hence, these systems use a hybrid of TDM and FDM.


Modulation

The shaping of a signal to convey information is known as modulation. Modulation can be used to represent a digital message as an analog waveform. This is commonly called keying (telecommunications), "keying"—a term derived from the older use of Morse Code in telecommunications—and several keying techniques exist (these include phase-shift keying, frequency-shift keying, and amplitude-shift keying). The "Bluetooth" system, for example, uses phase-shift keying to exchange information between various devices. In addition, there are combinations of phase-shift keying and amplitude-shift keying which is called (in the jargon of the field) "quadrature amplitude modulation" (QAM) that are used in high-capacity digital radio communication systems. Modulation can also be used to transmit the information of low-frequency analog signals at higher frequencies. This is helpful because low-frequency analog signals cannot be effectively transmitted over free space. Hence the information from a low-frequency analog signal must be impressed into a higher-frequency signal (known as the "carrier wave") before transmission. There are several different modulation schemes available to achieve this [two of the most basic being amplitude modulation (AM) and frequency modulation (FM)]. An example of this process is a disc jockey's voice being impressed into a 96 MHz carrier wave using frequency modulation (the voice would then be received on a radio as the channel "96 FM"). In addition, modulation has the advantage that it may use frequency division multiplexing (FDM).


Telecommunication networks

A telecommunications network is a collection of transmitters, receivers, and communications channels that send messages to one another. Some digital communications networks contain one or more Router (computing), routers that work together to transmit information to the correct user. An analog communications network consists of one or more telephone switch, switches that establish a connection between two or more users. For both types of networks, repeaters may be necessary to amplify or recreate the signal when it is being transmitted over long distances. This is to combat attenuation that can render the signal indistinguishable from the noise.ATIS Telecom Glossary 2000
, ATIS Committee T1A1 Performance and Signal Processing (approved by the American National Standards Institute), 28 February 2001.
Another advantage of digital systems over analog is that their output is easier to store in memory, i.e. two voltage states (high and low) are easier to store than a continuous range of states.


Societal impact

Telecommunication has a significant social, cultural and economic impact on modern society. In 2008, estimates placed the telecommunication industry's revenue at US$4.7 trillion or just under three percent of the gross world product (official exchange rate). Several following sections discuss the impact of telecommunication on society.


Microeconomics

On the Microeconomics, microeconomic scale, companies have used telecommunications to help build global business empires. This is self-evident in the case of online retailer Amazon.com but, according to academic Edward Lenert, even the conventional retailer Walmart has benefited from better telecommunication infrastructure compared to its competitors. In cities throughout the world, home owners use their telephones to order and arrange a variety of home services ranging from pizza deliveries to electricians. Even relatively poor communities have been noted to use telecommunication to their advantage. In Bangladesh's Narsingdi District, isolated villagers use cellular phones to speak directly to wholesalers and arrange a better price for their goods. In Ivory Coast, Côte d'Ivoire, coffee growers share mobile phones to follow hourly variations in coffee prices and sell at the best price.


Macroeconomics

On the Macroeconomics, macroeconomic scale, Lars-Hendrik Röller and Leonard Waverman suggested a causal link between good telecommunication infrastructure and economic growth. Few dispute the existence of a correlation although some argue it is wrong to view the relationship as causal. Because of the economic benefits of good telecommunication infrastructure, there is increasing worry about the inequitable access to telecommunication services amongst various countries of the world—this is known as the digital divide. A 2003 survey by the International Telecommunication Union (ITU) revealed that roughly a third of countries have fewer than one mobile subscription for every 20 people and one-third of countries have fewer than one land-line telephone subscription for every 20 people. In terms of Internet access, roughly half of all countries have fewer than one out of 20 people with Internet access. From this information, as well as educational data, the ITU was able to compile an index that measures the overall ability of citizens to access and use information and communication technologies. Using this measure, Sweden, Denmark and Iceland received the highest ranking while the African countries Nigeria, Burkina Faso and Mali received the lowest.


Social impact

Telecommunication has played a significant role in social relationships. Nevertheless, devices like the telephone system were originally advertised with an emphasis on the practical dimensions of the device (such as the ability to conduct business or order home services) as opposed to the social dimensions. It was not until the late 1920s and 1930s that the social dimensions of the device became a prominent theme in telephone advertisements. New promotions started appealing to consumers' emotions, stressing the importance of social conversations and staying connected to family and friends.Fischer, Claude S. Touch Someone': The Telephone Industry Discovers Sociability." Technology and Culture 29.1 (January 1988): 32–61. . . Since then the role that telecommunications has played in social relations has become increasingly important. In recent years, the popularity of social networking sites has increased dramatically. These sites allow users to communicate with each other as well as post photographs, events and profiles for others to see. The profiles can list a person's age, interests, sexual preference and relationship status. In this way, these sites can play important role in everything from organising social engagements to courtship. Prior to social networking sites, technologies like short message service (SMS) and the telephone also had a significant impact on social interactions. In 2000, market research group Ipsos MORI reported that 81% of 15- to 24-year-old SMS users in the United Kingdom had used the service to coordinate social arrangements and 42% to flirt.


Entertainment, news, and advertising

In cultural terms, telecommunication has increased the public's ability to access music and film. With television, people can watch films they have not seen before in their own home without having to travel to the video store or cinema. With radio and the Internet, people can listen to music they have not heard before without having to travel to the music store. Telecommunication has also transformed the way people receive their news. A 2006 survey (right table) of slightly more than 3,000 Americans by the non-profit Pew Internet and American Life Project in the United States the majority specified television or radio over newspapers. Telecommunication has had an equally significant impact on advertising. TNS Media Intelligence reported that in 2007, 58% of advertising expenditure in the United States was spent on media that depend upon telecommunication.


Regulation

Many countries have enacted legislation which conforms to the International Telecommunication Regulations established by the International Telecommunication Union (ITU), which is the "leading UN agency for information and communication technology issues". In 1947, at the Atlantic City Conference, the ITU decided to "afford international protection to all frequencies registered in a new international frequency list and used in conformity with the Radio Regulation". According to the ITU's ''Radio Regulations'' adopted in Atlantic City, all frequencies referenced in the ''International Frequency Registration Board'', examined by the board and registered on the ''International Frequency List'' "shall have the right to international protection from harmful interference". From a global perspective, there have been political debates and legislation regarding the management of telecommunication and broadcasting. The history of broadcasting discusses some debates in relation to balancing conventional communication such as printing and telecommunication such as radio broadcasting. The onset of
World War II World War II or the Second World War, often abbreviated as WWII or WW2, was a World war, global war that lasted from 1939 to 1945. It involved World War II by country, the vast majority of the world's countries—including all the great ...
brought on the first explosion of international broadcasting propaganda.Wood, James & Science Museum (Great Britain) "
History of international broadcasting
''". IET 1994, Volume 1, p. 2 of 258 . Republished by Google Books. Accessed 21 July 2009.
Countries, their governments, insurgents, terrorists, and militiamen have all used telecommunication and broadcasting techniques to promote propaganda. Patriotic propaganda for political movements and colonization started the mid-1930s. In 1936, the BBC broadcast propaganda to the Arab World to partly counter similar broadcasts from Italy, which also had colonial interests in North Africa. Modern insurgents, such as those in the latest Iraq War, often use intimidating telephone calls, SMSs and the distribution of sophisticated videos of an attack on coalition troops within hours of the operation. "The Sunni insurgents even have their own television station, Al-Zawraa TV, Al-Zawraa, which while banned by the Iraqi government, still broadcasts from Erbil, Iraqi Kurdistan, even as coalition pressure has forced it to switch satellite hosts several times."Garfield, Andrew.
The U.S. Counter-propaganda Failure in Iraq
", Fall 2007, ''The Middle East Quarterly'', Volume XIV: Number 4, Accessed 21 July 2009.
On 10 November 2014, Barack Obama, President Obama recommended the Federal Communications Commission reclassify Internet access, broadband Internet service as a telecommunications service to preserve net neutrality.


Modern media


Worldwide equipment sales

According to data collected by Gartner and Ars Technica sales of main consumer's telecommunication equipment worldwide in millions of units was:


Telephone

In a telephone network, the caller is connected to the person to whom they wish to talk by switches at various telephone exchanges. The switches form an electrical connection between the two users and the setting of these switches is determined electronically when the caller pulse dialing, dials the number. Once the connection is made, the caller's voice is transformed to an electrical signal using a small microphone in the caller's handset. This electrical signal is then sent through the network to the user at the other end where it is transformed back into sound by a small loudspeaker, speaker in that person's handset. As of 2015, the landline telephones in most residential homes are analog—that is, the speaker's voice directly determines the signal's voltage. Although short-distance calls may be handled from end-to-end as analog signals, increasingly telephone service providers are transparently converting the signals to digital signals for transmission. The advantage of this is that digitized voice data can travel side by side with data from the Internet and can be perfectly reproduced in long-distance communication (as opposed to analog signals that are inevitably impacted by noise). Mobile phones have had a significant impact on telephone networks. Mobile phone subscriptions now outnumber fixed-line subscriptions in many markets. Sales of mobile phones in 2005 totalled 816.6 million with that figure being almost equally shared amongst the markets of Asia/Pacific (204 m), Western Europe (164 m), CEMEA (Central Europe, the Middle East and Africa) (153.5 m), North America (148 m) and Latin America (102 m). In terms of new subscriptions over the five years from 1999, Africa has outpaced other markets with 58.2% growth. Increasingly these phones are being serviced by systems where the voice content is transmitted digitally such as GSM or W-CDMA with many markets choosing to deprecate analog systems such as Advanced Mobile Phone System, AMPS. There have also been dramatic changes in telephone communication behind the scenes. Starting with the operation of TAT-8 in 1988, the 1990s saw the widespread adoption of systems based on optical fibers. The benefit of communicating with optical fibers is that they offer a drastic increase in data capacity. TAT-8 itself was able to carry 10 times as many telephone calls as the last copper cable laid at that time and today's optical fibre cables are able to carry 25 times as many telephone calls as TAT-8. This increase in data capacity is due to several factors: First, optical fibres are physically much smaller than competing technologies. Second, they do not suffer from crosstalk (electronics), crosstalk which means several hundred of them can be easily bundled together in a single cable. Lastly, improvements in multiplexing have led to an exponential growth in the data capacity of a single fibre. Assisting communication across many modern optical fibre networks is a protocol known as Asynchronous Transfer Mode (ATM). The ATM protocol allows for the side-by-side data transmission mentioned in the second paragraph. It is suitable for public telephone networks because it establishes a pathway for data through the network and associates a traffic contract with that pathway. The traffic contract is essentially an agreement between the client and the network about how the network is to handle the data; if the network cannot meet the conditions of the traffic contract it does not accept the connection. This is important because telephone calls can negotiate a contract so as to guarantee themselves a constant bit rate, something that will ensure a caller's voice is not delayed in parts or cut off completely. There are competitors to ATM, such as Multiprotocol Label Switching (MPLS), that perform a similar task and are expected to supplant ATM in the future.


Radio and television

In a broadcast system, the central high-powered radio masts and towers, broadcast tower transmits a high-frequency electromagnetic wave to numerous low-powered receivers. The high-frequency wave sent by the tower is modulated with a signal containing visual or audio information. The receiver is then antenna tuner, tuned so as to pick up the high-frequency wave and a demodulator is used to retrieve the signal containing the visual or audio information. The broadcast signal can be either analog (signal is varied continuously with respect to the information) or digital (information is encoded as a set of discrete values). The broadcast media industry is at a critical turning point in its development, with many countries moving from analog to digital broadcasts. This move is made possible by the production of cheaper, faster and more capable integrated circuits. The chief advantage of digital broadcasts is that they prevent a number of complaints common to traditional analog broadcasts. For television, this includes the elimination of problems such as noise (video), snowy pictures, television interference (ghosting), ghosting and other distortion. These occur because of the nature of analog transmission, which means that perturbations due to noise will be evident in the final output. Digital transmission overcomes this problem because digital signals are reduced to discrete values upon reception and hence small perturbations do not affect the final output. In a simplified example, if a binary message 1011 was transmitted with signal amplitudes [1.0 0.0 1.0 1.0] and received with signal amplitudes [0.9 0.2 1.1 0.9] it would still decode to the binary message 1011— a perfect reproduction of what was sent. From this example, a problem with digital transmissions can also be seen in that if the noise is great enough it can significantly alter the decoded message. Using forward error correction a receiver can correct a handful of bit errors in the resulting message but too much noise will lead to incomprehensible output and hence a breakdown of the transmission. In digital television broadcasting, there are three competing standards that are likely to be adopted worldwide. These are the ATSC Standards, ATSC, Digital Video Broadcasting, DVB and ISDB standards; the adoption of these standards thus far is presented in the captioned map. All three standards use MPEG-2 for video compression. ATSC uses Dolby Digital AC-3 for audio compression, ISDB uses Advanced Audio Coding (MPEG-2 Part 7) and DVB has no standard for audio compression but typically uses MPEG-1 Part 3 Layer 2. The choice of modulation also varies between the schemes. In digital audio broadcasting, standards are much more unified with practically all countries choosing to adopt the Digital Audio Broadcasting standard (also known as the Eureka 147 standard). The exception is the United States which has chosen to adopt HD Radio. HD Radio, unlike Eureka 147, is based upon a transmission method known as in-band on-channel transmission that allows digital information to "piggyback" on normal AM or FM analog transmissions. However, despite the pending switch to digital, analog television remains being transmitted in most countries. An exception is the United States that ended analog television transmission (by all but the very low-power TV stations) on 12 June 2009 after twice delaying the switchover deadline. Kenya also ended analog television transmission in December 2014 after multiple delays. For analog television, there were three standards in use for broadcasting color TV (see a map on adoption :File:NTSC-PAL-SECAM.png, here). These are known as PAL (German designed), NTSC (American designed), and SECAM (French-designed). For analog radio, the switch to digital radio is made more difficult by the higher cost of digital receivers. The choice of modulation for analog radio is typically between amplitude (AM) or frequency modulation (FM). To achieve stereophonic sound, stereo playback, an amplitude modulated subcarrier is used for stereo FM, and quadrature amplitude modulation is used for stereo AM or C-QUAM.


Internet

The Internet is a worldwide network of computers and computer networks that communicate with each other using the Internet Protocol (IP). Any computer on the Internet has a unique IP address that can be used by other computers to route information to it. Hence, any computer on the Internet can send a message to any other computer using its IP address. These messages carry with them the originating computer's IP address allowing for two-way communication. The Internet is thus an exchange of messages between computers. It is estimated that 51% of the information flowing through two-way telecommunications networks in the year 2000 were flowing through the Internet (most of the rest (42%) through the landline telephone). By the year 2007 the Internet clearly dominated and captured 97% of all the information in telecommunication networks (most of the rest (2%) through mobile phones). , an estimated 21.9% of the world population has access to the Internet with the highest access rates (measured as a percentage of the population) in North America (73.6%), Oceania/Australia (59.5%) and Europe (48.1%). In terms of Broadband Internet access, broadband access, Iceland (26.7%), South Korea (25.4%) and the Netherlands (25.3%) led the world. The Internet works in part because of communications protocol, protocols that govern how the computers and routers communicate with each other. The nature of computer network communication lends itself to a layered approach where individual protocols in the protocol stack run more-or-less independently of other protocols. This allows lower-level protocols to be customized for the network situation while not changing the way higher-level protocols operate. A practical example of why this is important is because it allows an Internet browser to run the same code regardless of whether the computer it is running on is connected to the Internet through an Ethernet or Wi-Fi connection. Protocols are often talked about in terms of their place in the OSI reference model (pictured on the right), which emerged in 1983 as the first step in an unsuccessful attempt to build a universally adopted networking protocol suite. For the Internet, the physical medium and data link protocol can vary several times as packets traverse the globe. This is because the Internet places no constraints on what physical medium or data link protocol is used. This leads to the adoption of media and protocols that best suit the local network situation. In practice, most intercontinental communication will use the Asynchronous Transfer Mode (ATM) protocol (or a modern equivalent) on top of optic fiber. This is because for most intercontinental communication the Internet shares the same infrastructure as the public switched telephone network. At the network layer, things become standardized with the Internet Protocol (IP) being adopted for logical addressing. For the World Wide Web, these "IP addresses" are derived from the human-readable form using the Domain Name System (e.g. 72.14.207.99 is derived from www.google.com). At the moment, the most widely used version of the Internet Protocol is version four but a move to version six is imminent. At the transport layer, most communication adopts either the Transmission Control Protocol (TCP) or the User Datagram Protocol (UDP). TCP is used when it is essential every message sent is received by the other computer whereas UDP is used when it is merely desirable. With TCP, packets are retransmitted if they are lost and placed in order before they are presented to higher layers. With UDP, packets are not ordered nor retransmitted if lost. Both TCP and UDP packets carry TCP and UDP port, port numbers with them to specify what application or process (computing), process the packet should be handled by. Because certain application-level protocols use List of TCP and UDP port numbers, certain ports, network administrators can manipulate traffic to suit particular requirements. Examples are to restrict Internet access by blocking the traffic destined for a particular port or to affect the performance of certain applications by assigning WAN optimization, priority. Above the transport layer, there are certain protocols that are sometimes used and loosely fit in the session and presentation layers, most notably the Secure Sockets Layer (SSL) and Transport Layer Security (TLS) protocols. These protocols ensure that data transferred between two parties remains completely confidential. Finally, at the application layer, are many of the protocols Internet users would be familiar with such as HTTP (web browsing), POP3 (e-mail), File Transfer Protocol, FTP (file transfer), IRC (Internet chat), BitTorrent (protocol), BitTorrent (file sharing) and XMPP (instant messaging). VoIP, Voice over Internet Protocol (VoIP) allows data packets to be used for synchronous voice communications. The data packets are marked as voice type packets and can be prioritized by the network administrators so that the real-time, synchronous conversation is less subject to contention with other types of data traffic which can be delayed (i.e. file transfer or email) or buffered in advance (i.e. audio and video) without detriment. That prioritization is fine when the network has sufficient capacity for all the VoIP calls taking place at the same time and the network is enabled for prioritization i.e. a private corporate-style network, but the Internet is not generally managed in this way and so there can be a big difference in the quality of VoIP calls over a private network and over the public Internet.


Local area networks and wide area networks

Despite the growth of the Internet, the characteristics of local area networks (LANs)—computer networks that do not extend beyond a few kilometers—remain distinct. This is because networks on this scale do not require all the features associated with larger networks and are often more cost-effective and efficient without them. When they are not connected with the Internet, they also have the advantages of privacy and security. However, purposefully lacking a direct connection to the Internet does not provide assured protection from hackers, military forces, or economic powers. These threats exist if there are any methods for connecting remotely to the LAN. Wide area networks (WANs) are private computer networks that may extend for thousands of kilometers. Once again, some of their advantages include privacy and security. Prime users of private LANs and WANs include armed forces and intelligence agencies that must keep their information secure and secret. In the mid-1980s, several sets of communication protocols emerged to fill the gaps between the data-link layer and the application layer of the OSI reference model. These included Appletalk, IPX, and NetBIOS with the dominant protocol set during the early 1990s being IPX due to its popularity with MS-DOS users. TCP/IP existed at this point, but it was typically only used by large government and research facilities. As the Internet grew in popularity and its traffic was required to be routed into private networks, the TCP/IP protocols replaced existing local area network technologies. Additional technologies, such as DHCP, allowed TCP/IP-based computers to self-configure in the network. Such functions also existed in the AppleTalk/ IPX/ NetBIOS protocol sets. Whereas Asynchronous Transfer Mode (ATM) or Multiprotocol Label Switching (MPLS) are typical data-link protocols for larger networks such as WANs; Ethernet and Token Ring are typical data-link protocols for LANs. These protocols differ from the former protocols in that they are simpler, e.g., they omit features such as quality of service guarantees, and offer carrier sense multiple access with collision detection, collision prevention. Both of these differences allow for more economical systems. Despite the modest popularity of Token Ring in the 1980s and 1990s, virtually all LANs now use either wired or wireless Ethernet facilities. At the physical layer, most wired Ethernet implementations use twisted pair, copper twisted-pair cables (including the common 10BASE-T networks). However, some early implementations used heavier coaxial cables and some recent implementations (especially high-speed ones) use optical fibers. When optic fibers are used, the distinction must be made between multimode fibers and single-mode fibers. Multi-mode optical fiber, Multimode fibers can be thought of as thicker optical fibers that are cheaper to manufacture devices for, but that suffer from less usable bandwidth and worse attenuation—implying poorer long-distance performance.Fiber Optic Cable Tutorial
, Arc Electronics. Retrieved June 2007.


See also


References


Citations


Bibliography

* Gerard Goggin, Goggin, Gerard, ''Global Mobile Media'' (New York: Routledge, 2011), p. 176. . * Organisation for Economic Co-operation and Development, OECD
''Universal Service and Rate Restructuring in Telecommunications''
Organisation for Economic Co-operation and Development (OECD) Publishing, 1991. . * Wheen, Andrew. ''Dot-Dash to Dot.Com: How Modern Telecommunications Evolved from the Telegraph to the Internet'' (Springer, 2011).


External links


International Teletraffic Congress

International Telecommunication Union (ITU)

ATIS Telecom Glossary

Federal Communications Commission

IEEE Communications Society

International Telecommunication Union
* (Ericsson removed the book from their site in September 2005) {{Authority control Economics of transport and utility industries Mass media technology Telecommunications, ja:通信