Telecommunication

Copy of the original phone of Alexander Graham Bell at the Musée des Arts et Métiers in Paris

"Telecom" redirects here. WikipediaWikiProject Aircraft. Please see WikipediaWikiProject Aircraft/page content for recommended layout The Musée des Arts et Métiers is a museum in Paris that houses the collection of the Conservatoire National des Arts et Métiers, which was founded in 1794 For specific telecommunications companies, see List of telephone operating companies. Countries by alphabetical order A Afghanistan Albania Algeria

Telecommunication is the assisted transmission of signals over a distance for the purpose of communication. In Telecommunications transmission is the process of sending propagating and receiving an analogue or digital information signal over a physical point-to-point or In the fields of communications, Signal processing, and in Electrical engineering more generally a signal is any time-varying or spatial-varying quantity Communication is the process of conveying information from a sender to a receiver with the use of a medium in which the communicated information is understood the same way In earlier times, this may have involved the use of smoke signals, drums, semaphore, flags, or heliograph. The smoke signal is one of the oldest forms of communication in recorded history Developed and used by Cultures living in Forested areas drums served as an early form of long distance Communication, and were used during ceremonial A semaphore telegraph, optical telegraph, shutter telegraph chain, Chappe telegraph, or Napoleonic semaphore is a system Flag signals can mean any of various methods of using flags or pennants to send signals Flaghoist signalling or the flaghoist signalling system uses sets of flags A Heliograph (from the Greek Helios ( Ἥλιος meaning "sun" and graphein (γραφειν = write is a wireless In modern times, telecommunication typically involves the use of electronic transmitters such as the telephone, television, radio or computer. Basic principle A traditional landline telephone system also known as "plain old telephone service" (POTS, commonly handles both signaling and audio information Television ( TV) is a widely used Telecommunication medium for sending ( Broadcasting) and receiving moving Images, either monochromatic Radio is the transmission of signals by Modulation of electromagnetic waves with frequencies below those of visible Light. A computer is a Machine that manipulates data according to a list of instructions. Early inventors in the field of telecommunication include Antonio Meucci, Alexander Graham Bell, Guglielmo Marconi and John Logie Baird. Antonio Meucci ( Florence, April 13, 1808 &ndash October 18, 1889) was an Italian -born inventor who developed a form of WikipediaWikiProject Aircraft. Please see WikipediaWikiProject Aircraft/page content for recommended layout Marchese Guglielmo Marconi mar'koni (25 April 1874 – 20 July 1937 was an Italian inventor best known for his development of a Radiotelegraph system John Logie Baird (August 13 1888 – June 14 1946 was a Scottish engineer and inventor of the world's first working television system Telecommunication is an important part of the world economy and the telecommunication industry's revenue has been placed at just under 3 percent of the gross world product. Gross world product (GWP is the total Gross national product of all the countries in the world

Key concepts

Etymology

The word telecommunication was adapted from the French word télécommunication. It is a compound of the Greek prefix tele- (τηλε-), meaning 'far off', and the Latin communicare, meaning 'to share'. ^[1] The French word télécommunication was coined in 1904 by French engineer and novelist Édouard Estaunié. Édouard Estaunié ( Dijon, February 4 1862 - Paris, February 1[[ 942]] was a French novelist ^[2]

Basic elements

A telecommunication system consists of three basic elements:

a transmitter that takes information and converts it to a signal;
a transmission medium that carries the signal; and,
a receiver that receives the signal and converts it back into usable information. For biologic transmitters see Transmitter substance. A transmitter is an electronic device which usually with the aid of an antenna Information as a concept has a diversity of meanings from everyday usage to technical settings In the fields of communications, Signal processing, and in Electrical engineering more generally a signal is any time-varying or spatial-varying quantity A transmission medium' (plural transmission media) is a material substance ( Solid, Liquid or Gas) which can propagate This article is about a radio receiver for other uses see Radio (disambiguation.

For example, in a radio broadcast the broadcast tower is the transmitter, free space is the transmission medium and the radio is the receiver. Radio masts and towers are typically tall structures designed In Classical physics, free space is a concept of Electromagnetic theory, corresponding to a theoretically "perfect" Vacuum, and sometimes Radio is the transmission of signals by Modulation of electromagnetic waves with frequencies below those of visible Light. Often telecommunication systems are two-way with a single device acting as both a transmitter and receiver or transceiver. For example, a mobile phone is a transceiver. ^[3]

Telecommunication over a phone line is called point-to-point communication because it is between one transmitter and one receiver. Point-to-point telecommunications generally refers to a connection restricted to two endpoints usually host computers Telecommunication through radio broadcasts is called broadcast communication because it is between one powerful transmitter and numerous receivers. For the band see Broadcast (band Broadcasting is the distribution of audio and/or Video signals which transmit ^[3]

Analogue or digital

Signals can be either analogue or digital. An analog or analogue signal is any continuous signal for which the time varying feature (variable of the signal is a representation of some other A digital system uses discrete (discontinuous values usually but not always Symbolized Numerically (hence called "digital" to represent information for In an analogue 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 ones and zeros). During transmission the information contained in analogue signals will be degraded by noise. Conversely, unless the noise exceeds a certain threshold, the information contained in digital signals will remain intact. This noise resistance represents a key advantage of digital signals over analogue signals. ^[4]

Networks

A collection of transmitters, receivers or transceivers that communicate with each other is known as a network. A telecommunications network is a network of Telecommunications links and nodes arranged so that messages may be passed from one part of the network to another over Digital networks may consist of one or more routers that route information to the correct user. A router ('rautər in the USA 'rutər in the UK and Ireland, or either pronunciation in Australia and Canada is a Computer whose software and hardware are usually An analogue network may consist of one or more switches that establish a connection between two or more users. In the field of Telecommunications, a telephone exchange or telephone switch is a system of electronic components that connects telephone calls For both types of network, repeaters may be necessary to amplify or recreate the signal when it is being transmitted over long distances. A repeater is an electronic device that receives a signal and Retransmits it at a higher level and/or higher power or onto the other side of an obstruction This is to combat attenuation that can render the signal indistinguishable from noise. In Physics, attenuation (in some context also called extinction) is the gradual loss in intensity of any kind of Flux through a medium is a one volume manga created by Tsutomu Nihei as a prequel to his ten-volume work Blame!. ^[5]

Channels

A channel is a division in a transmission medium so that it can be used to send multiple streams of information. Channel, in communications (sometimes called communications channel) refers to the medium used to convey Information from a For example, a radio station may broadcast at 96. 1 MHz while another radio station may broadcast at 94. 5 MHz. In this case, the medium has been divided by frequency and each channel has received a separate frequency to broadcast on. Frequency is a measure of the number of occurrences of a repeating event per unit Time. Alternatively, one could allocate each channel a recurring segment of time over which to broadcast — this is known as time-division multiplexing and is sometimes used in digital communication. Time-Division Multiplexing ( TDM) is a type of Digital or (rarely analog Multiplexing in which two or more signals or bit streams are transferred ^[5]

Modulation

The shaping of a signal to convey information is known as modulation. In Telecommunications, modulation is the process of varying a periodic Waveform, i Modulation can be used to represent a digital message as an analogue waveform. This is known as keying and several keying techniques exist (these include phase-shift keying, frequency-shift keying and amplitude-shift keying). Phase-shift keying (PSK is a Digital Modulation scheme that conveys data by changing or modulating the phase of a reference signal Frequency-shift keying (FSK is a Frequency modulation scheme in which digital information is transmitted through discrete frequency changes of a Carrier wave Amplitude-shift keying ( ASK) is a form of Modulation that represents Digital Data as variations in the Amplitude of a Carrier Bluetooth, for example, uses phase-shift keying to exchange information between devices. Bluetooth is a wireless protocol utilizing short-range communications technology facilitating data transmission over short distances from fixed and/or mobile devices creating wireless Phase-shift keying (PSK is a Digital Modulation scheme that conveys data by changing or modulating the phase of a reference signal ^[6]^[7]

Modulation can also be used to transmit the information of analogue signals at higher frequencies. This is helpful because low-frequency analogue signals cannot be effectively transmitted over free space. Hence the information from a low-frequency analogue signal must be superimposed on a higher-frequency signal (known as a carrier wave) before transmission. In Telecommunications, a carrier wave, or carrier is a Waveform (usually Sinusoidal) that is modulated (modified with an input signal There are several different modulation schemes available to achieve this (two of the most basic being amplitude modulation and frequency modulation). Amplitude modulation ( AM) is a technique used in electronic communication most commonly for transmitting information via a Radio Carrier wave An example of this process is a DJ's voice being superimposed on a 96 MHz carrier wave using frequency modulation (the voice would then be received on a radio as the channel “96 FM”). A disc jockey (also known as DJ or deejay) is a person who selects and plays recorded music for an audience ^[8]

Society and telecommunication

Telecommunication is an important part of modern society. In 2006, estimates placed the telecommunication industry's revenue at $1. 2 trillion or just under 3% of the gross world product (official exchange rate). Gross world product (GWP is the total Gross national product of all the countries in the world ^[9]

On the microeconomic scale, companies have used telecommunication to help build global empires. This is self-evident in the case of online retailer Amazon.com but, according to academic Edward Lenert, even the conventional retailer Wal-Mart has benefited from better telecommunication infrastructure compared to its competitors. Amazoncom Inc ( is an American electronic commerce ( E-commerce) company in Seattle Washington. Wal-Mart Stores Inc (or Walmart as written in its new logo is an American public corporation that runs a chain of large discount department stores ^[10] In cities throughout the world, home owners use their telephones to organize many home services ranging from pizza deliveries to electricians. Basic principle A traditional landline telephone system also known as "plain old telephone service" (POTS, commonly handles both signaling and audio information Pizza delivery is a service in which a pizzeria delivers a Pizza, usually ordered by telephone or Internet to a customer An electrician is a Tradesman specializing in electrical wiring of buildings and related equipment Even relatively poor communities have been noted to use telecommunication to their advantage. In Bangladesh's Narshingdi district, isolated villagers use cell phones to speak directly to wholesalers and arrange a better price for their goods. ( Bengali: বাংলাদেশ inc-Latn Bangladesh) officially In Cote d'Ivoire, coffee growers share mobile phones to follow hourly variations in coffee prices and sell at the best price. Côte d'Ivoire (ˌkoʊt divˈwɑː(r ' in English, kot diˈvwaʀ in French) or Ivory Coast, officially the Republic of Côte d'Ivoire, is a ^[11]

On the macroeconomic scale, Lars-Hendrik Röller and Leonard Waverman suggested a causal link between good telecommunication infrastructure and economic growth. ^[12] Few dispute the existence of a correlation although some argue it is wrong to view the relationship as causal. ^[13]

Due to the economic benefits of good telecommunication infrastructure, there is increasing worry about the digital divide. The term digital divide refers to the gap between those people with effective access to Digital and Information technology and those without This is because the world's population does not have equal access to telecommunication systems. A 2003 survey by the International Telecommunication Union (ITU) revealed that roughly one-third of countries have less than 1 mobile subscription for every 20 people and one-third of countries have less than 1 fixed line subscription for every 20 people. In terms of Internet access, roughly half of all countries have less than 1 in 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. ^[14] Using this measure, Sweden, Denmark and Iceland received the highest ranking while the African countries Niger, Burkina Faso and Mali received the lowest. "Sverige" redirects here For other uses see Sweden (disambiguation and Sverige (disambiguation. The Kingdom of Denmark ( ˈd̥ænmɑɡ̊ (archaic ˈd̥anmɑːɡ̊ commonly known as Denmark, is a country in the Scandinavian region of northern Europe Iceland, officially the Republic of Iceland ( ( Ísland or Lýðveldið Ísland ( Niger ( or /ˈnaɪdʒɚ/) officially the Republic of Niger, is a Landlocked country in Western Africa, named after the Niger River. Burkina Faso (bɚˌkiːnəˈfɑːsoʊ burr-KEE-na FAH-soh) also known by its short-form name Burkina, is a Landlocked nation in West Africa Mali, officially the Republic of Mali (République du Mali is a Landlocked nation in Western Africa. ^[15]

History

For more details on this topic, see History of telecommunication. The history of telecommunication began with the use of Smoke signals and drums in Africa, the Americas and parts of Asia.

Early telecommunications

A replica of one of Chappe's semaphore towers.

Early forms of telecommunication include smoke signals and drums. The smoke signal is one of the oldest forms of communication in recorded history Developed and used by Cultures living in Forested areas drums served as an early form of long distance Communication, and were used during ceremonial Drums were used by natives in Africa, New Guinea and South America whereas smoke signals were used by natives in North America and China. New Guinea, located just north of Australia, is the world's second largest island, having become separated from the Australian mainland when the area now known South America is a Continent of the Americas, situated entirely in the Western Hemisphere and mostly in the Southern Hemisphere, with a China ( Wade-Giles ( Mandarin) Chung¹kuo² is a cultural region, an ancient Civilization, and depending on perspective a National Contrary to what one might think, these systems were often used to do more than merely announce the presence of a camp. ^[16]^[17]

In the Middle Ages, chains of beacons were commonly used on hilltops as a means of relaying a signal. Beacons are aids to Navigation devices Intentionally conspicuous beacons help guide navigators to their destinations 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. The Spanish Armada ( Spanish: Grande y Felicísima Armada, "Great and Most Fortunate Navy" or Armada Invencible, "Invincible Plymouth ( is a city and unitary authority area on the coast of Devon, England about south west of London. London ( ˈlʌndən is the capital and largest urban area in the United Kingdom. ^[18]

Homing pigeons have been often been used through history in different cultures. The homing pigeon is a variety of domesticated Rock Pigeon ( Columba livia domestica) that has been selectively Pigeon post is thought to have Persians roots, and was also used by the Romans to aid their military. Pigeon post is the use of Homing pigeons to carry messages As a method of communication it is likely as old as the ancient Persians from whom the art of training Frontinus said that Julius Ceasar used pigeons as messengers in his conquest of Gaul. Sextus Julius Frontinus (ca 40-103 AD was one of the most distinguished Roman aristocrats of the late first century AD but is best known to the post-Classical world as an Gaul (Gallia was the Roman name for the region of Western Europe comprising present day northern Italy, France, Belgium, western ^[19] The Greeks conveyed the names of the victors at the Olympic Games to their various cities by this means. The Greeks ( Greek: Έλληνες) are a Nation and Ethnic group native to Greece, Cyprus and neighbouring regions ^[20] Before the electrical telegraph, this method of communication was used among stockbrokers and financiers. A stock broker or stockbroker is a qualified and regulated professional who buys and sells shares and other securities through Market makers or The Dutch government used the system in Java and Sumatra early in the 19th century, the birds being obtained from Baghdad. Java (Jawa is an Island of Indonesia and the site of its Capital city Jakarta. Sumatra (also spelled Sumatera) is the sixth largest island in the world (approximately 470000 km² and is the largest island entirely in Indonesia (two Baghdad (بغداد) is the Capital of Iraq and of Baghdad Governorate, with which it is also coterminous Reuter started in 1849 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. Paul Julius Baron von Reuter ( July 21, 1816 - February 25, 1899) was a German -born British journalist and media owner ( Ripuarian: Oche, Dutch: Aken, Spanish: Aquisgrán, Italian: Aquisgrana, French, Brussels (Bruxelles pronounced; Brussel pronounced) officially the Brussels Capital-Region, is ^[21]

In 1792, Claude Chappe, a French engineer, built the first fixed visual telegraphy system (or semaphore line) between Lille and Paris. Claude Chappe ( December 25, 1763 &ndash January 23, 1805) was a French inventor who in 1792 demonstrated a practical semaphore system A semaphore telegraph, optical telegraph, shutter telegraph chain, Chappe telegraph, or Napoleonic semaphore is a system Lille (lil Rijsel is a city in northern France. It is the principal city of the Lille Métropole, the fourth-largest Metropolitan area in the country Paris (ˈpærɨs in English; in French) is the Capital of France and the country's largest city ^[22] 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. ^[23]

Telegraph and telephone

The first commercial electrical telegraph was constructed by Sir Charles Wheatstone and Sir William Fothergill Cooke and opened on 9 April 1839. The electrical telegraph is a telegraph that uses electric signals The electromagnetic telegraph is a device for human-to-human transmission Sir Charles Wheatstone FRS (6 February 1802 - 19 October 1875 was a British Scientist and Inventor of many scientific breakthroughs Sir William Fothergill Cooke ( 4 May 1806 &ndash 25 June 1879) was with Charles Wheatstone, the co-inventor of the Cooke-Wheatstone Events 193 - Septimius Severus is proclaimed Roman Emperor by the army in Illyricum (in the Balkans) Year 1839 ( MDCCCXXXIX) was a Common year starting on Tuesday (link will display the full calendar of the Gregorian Calendar (or a Common Both Wheatstone and Cooke viewed their device as "an improvement to the [existing] electromagnetic telegraph" not as a new device. ^[24]

Samuel Morse independently developed a version of the electrical telegraph that he unsuccessfully demonstrated on 2 September 1837. Samuel Finley Breese Morse ( April 27, 1791 &ndash April 2, 1872) was an American painter of portraits and historic Events 44 BC - Pharaoh Cleopatra VII of Egypt declares her son co-ruler as Ptolemy XV Caesarion. Year 1837 ( MDCCCXXXVII) was a Common year starting on Sunday (link will display the full calendar of the Gregorian Calendar (or a Common His code was an important advance over Wheatstone's signaling method. Morse code is a Character encoding for transmitting telegraphic information using standardized sequences of short and long elements to represent the letters numerals The first transatlantic telegraph cable was successfully completed on 27 July 1866, allowing transatlantic telecommunication for the first time. The first transatlantic Telegraph Cable crossed the Atlantic Ocean from Foilhommerum Valentia Island, in western Ireland to Events 1214 - Battle of Bouvines: In France, Philip II of France defeats John of England. Year 1866 ( MDCCCLXVI) was a Common year starting on Monday (link will display the full calendar of the Gregorian calendar (or a Common ^[25]

The conventional telephone was invented independently by Alexander Bell and Elisha Gray in 1876. WikipediaWikiProject Aircraft. Please see WikipediaWikiProject Aircraft/page content for recommended layout Elisha Gray (August 2 1835 &ndash January 21 1901 was an American electrical engineer and is best known for his development of a telephone prototype in 1876 in ^[26] Antonio Meucci invented the first device that allowed the electrical transmission of voice over a line in 1849. Antonio Meucci ( Florence, April 13, 1808 &ndash October 18, 1889) was an Italian -born inventor who developed a form of However Meucci's device was of little practical value because it relied upon the electrophonic effect and thus required users to place the receiver in their mouth to “hear” what was being said. The microwave auditory effect, also known as the microwave hearing effect or the Frey effect, consists of audible clicks induced by pulsed/modulated Microwave ^[27] The first commercial telephone services were set-up in 1878 and 1879 on both sides of the Atlantic in the cities of New Haven and London. London ( ˈlʌndən is the capital and largest urban area in the United Kingdom. ^[28]^[29]

Radio and television

In 1832, James Lindsay gave a classroom demonstration of wireless telegraphy to his students. James Bowman Lindsay ( September 8 1799 - June 29 1862) was a Scottish inventor and author The term Wireless Telegraphy is a historic term used today as applied to early Radio Telegraph communications techniques and practices By 1854, he was able to demonstrate a transmission across the Firth of Tay from Dundee, Scotland to Woodhaven, a distance of two miles (3 km), using water as the transmission medium. The Firth of Tay ( Scottish Gaelic: Linne Tatha) is a Firth in Scotland between the Council areas of Fife, Perth and Dundee (Dùn Dèagh is the fourth-largest city in Scotland and fully named as Dundee City, one of Scotland's 32 local government council Woodhaven used to be a small village between Newport-on-Tay and Wormit in Fife, Scotland but over the years due to expansion of both these villages ^[30] In December 1901, Guglielmo Marconi established wireless communication between St. John's, Newfoundland (Canada) and Poldhu, Cornwall (England), earning him the 1909 Nobel Prize in physics (which he shared with Karl Braun). Marchese Guglielmo Marconi mar'koni (25 April 1874 – 20 July 1937 was an Italian inventor best known for his development of a Radiotelegraph system St John's (ˌseɪntˈdʒanz French Saint-Jean) is the provincial capital of Newfoundland and Labrador, Canada and located on the eastern tip Poldhu is a small area in south Cornwall, England, UK, situated on the Lizard Peninsula it comprises Poldhu Point and Poldhu Cove The Nobel Prize in Physics (Nobelpriset i fysik is awarded once a year by the Royal Swedish Academy of Sciences. Karl Ferdinand Braun ( 6 June 1850 in Fulda, Germany &ndash 20 April 1918 in New York City, U ^[31] However small-scale radio communication had already been demonstrated in 1893 by Nikola Tesla in a presentation to the National Electric Light Association. There have already been discussions about Tesla's ethnicity on the talk page ^[32]

On March 25, 1925, John Logie Baird was able to demonstrate the transmission of moving pictures at the London department store Selfridges. Events 1199 - Richard I is wounded by a crossbow bolt while fighting France which leads to his death on April 6. Year 1925 ( MCMXXV) was a Common year starting on Thursday (link will display the full calendar of the Gregorian calendar. John Logie Baird (August 13 1888 – June 14 1946 was a Scottish engineer and inventor of the world's first working television system Selfridges is a chain of Department stores in the United Kingdom. Baird's device relied upon the Nipkow disk and thus became known as the mechanical television. A Nipkow disk (sometimes Anglicized as Nipkov disk also known as scanning disk, is a mechanical geometrically operating Image scanning device invented by Mechanical television was a Television system that used mechanical or Electromechanical devices to capture and display images It formed the basis of experimental broadcasts done by the British Broadcasting Corporation beginning September 30, 1929. Events 1399 - Henry IV is proclaimed King of England. 1744 - France and Spain defeat the Year 1929 ( MCMXXIX) was a Common year starting on Tuesday (link will display the full calendar of the Gregorian calendar. ^[33] However, for most of the twentieth century televisions depended upon the cathode ray tube invented by Karl Braun. Karl Ferdinand Braun ( 6 June 1850 in Fulda, Germany &ndash 20 April 1918 in New York City, U The first version of such a television to show promise was produced by Philo Farnsworth and demonstrated to his family on September 7, 1927. Philo Taylor Farnsworth ( August 19, 1906 – March 11, 1971) was an American inventor Events 1251 BC - A Solar eclipse on this date might mark the birth of legendary Heracles at Thebes Greece. Year 1927 ( MCMXXVII) was a Common year starting on Saturday (link will display full calendar of the Gregorian calendar. ^[34]

Computer networks and the Internet

On September 11, 1940, George Stibitz was able to transmit problems using teletype to his Complex Number Calculator in New York and receive the computed results back at Dartmouth College in New Hampshire. Events 9 - The Battle of the Teutoburg Forest ends 506 - The Bishops of Visigothic Gaul Year 1940 ( MCMXL) was a Leap year starting on Monday (link will display the full 1940 calendar of the Gregorian calendar. George Robert Stibitz ( April 20, 1904 &ndash January 31, 1995) is internationally recognized as a father of the modern digital computer A teleprinter ( New York ( is a state in the Mid-Atlantic and Northeastern regions of the United States and is the nation's third most populous Dartmouth College ( is a private, Coeducational University located in Hanover, New Hampshire, U New Hampshire ( is a state in the New England region of the northeastern United States of America. ^[35] This configuration of a centralized computer or mainframe with remote dumb terminals remained popular throughout the 1950s. Mainframes (often colloquially referred to as Big Iron) are Computers used mainly by large organizations for critical applications typically bulk data However, it was not until the 1960s that researchers started to investigate packet switching — a technology that would allow chunks of data to be sent to different computers without first passing through a centralized mainframe. Packet switching is a network communications method that splits data traffic (digital representations of text sound or video data into chunks called packets, that are then A four-node network emerged on December 5, 1969; this network would become ARPANET, which by 1981 would consist of 213 nodes. Events 63 BC - Cicero reads the last of his Catiline Orations. Year 1969 ( MCMLXIX) was a Common year starting on Wednesday (link will display full calendar of the Gregorian calendar. The ARPANET ( Advanced Research Projects Agency Network) developed by ARPA of the United States Department of Defense, was the world's first operational ^[36]

ARPANET's development centred around the Request for Comment process and on April 7, 1969, RFC 1 was published. In Computer network Engineering, a Request for Comments (RFC is a Memorandum published by the Internet Engineering Task Force (IETF describing Events 529 - First draft of Corpus Juris Civilis (a fundamental work in Jurisprudence) is issued by Eastern Roman Emperor Year 1969 ( MCMLXIX) was a Common year starting on Wednesday (link will display full calendar of the Gregorian calendar. This process is important because ARPANET would eventually merge with other networks to form the Internet and many of the protocols the Internet relies upon today were specified through the Request for Comment process. The Internet is a global system of interconnected Computer networks In September 1981, RFC 791 introduced the Internet Protocol v4 (IPv4) and RFC 793 introduced the Transmission Control Protocol (TCP) — thus creating the TCP/IP protocol that much of the Internet relies upon today. The Internet Protocol ( IP) is a protocol used for communicating data across a Packet-switched Internetwork using the Internet Protocol The Transmission Control Protocol (TCP is one of the core protocols of the Internet Protocol Suite. The Internet is a global system of interconnected Computer networks

However, not all important developments were made through the Request for Comment process. Two popular link protocols for local area networks (LANs) also appeared in the 1970s. A patent for the token ring protocol was filed by Olof Soderblom on October 29, 1974 and a paper on the Ethernet protocol was published by Robert Metcalfe and David Boggs in the July 1976 issue of Communications of the ACM. Token ring Local area network (LAN technology is a local area network protocol which resides at the Data link layer Olof Söderblom, born 1940, is the creator of Token ring networking and grandson of Nathan Söderblom, recipient of the 1930 Nobel Peace Prize Events 437 - Valentinian III, Western Roman Emperor, marries Licinia Eudoxia, daughter of his cousin Theodosius II Year 1974 ( MCMLXXIV) was a Common year starting on Tuesday (link will display full calendar of the 1974 Gregorian calendar. Ethernet is a family of frame -based Computer networking technologies for Local area networks (LANs Robert Melancton Metcalfe (born April 7, 1946 in Brooklyn, New York) is an electrical engineer from the United States who co-invented Ethernet David Reeves Boggs is an electrical and radio engineer from the United States who developed early prototypes of Internet protocols File servers Communications of the ACM ( CACM) is the flagship monthly Journal of the Association for Computing Machinery (ACM ^[37]^[38]

Modern operation

Telephone

Optical fibre provides cheaper bandwidth for long distance communication

In an analogue telephone network, the caller is connected to the person he wants to talk to by switches at various telephone exchanges. An optical fiber (or fibre) is a Glass or Plastic fiber that carries Light along its length The calling party (also called caller, call originator or A-party) is a person who (or device that Initiates a Telephone call over In the field of Telecommunications, a telephone exchange or telephone switch is a system of electronic components that connects telephone calls The switches form an electrical connection between the two users and the setting of these switches is determined electronically when the caller dials the number. Pulse dialing, dial pulse, or loop disconnect dialing, also called Rotary or Decadic dialling in the United Kingdom (because up to 10 pulses Once the connection is made, the caller's voice is transformed to an electrical signal using a small microphone in the caller's handset. A transceiver is a device that has both a Transmitter and a receiver which are combined and share common circuitry or a single housing This electrical signal is then sent through the network to the user at the other end where it transformed back into sound by a small speaker in that person's handset. For the Marty Friedman album see Loudspeaker (album A loudspeaker, speaker, or speaker system is an electroacoustical There is a separate electrical connection that works in reverse, allowing the users to converse. ^[39]^[40]

The fixed-line telephones in most residential homes are analogue — that is, the speaker's voice directly determines the signal's voltage. A landline, main line or fixed-line is a Telephone line which travels through a solid medium either metal Wire or Optical fibre Although short-distance calls may be handled from end-to-end as analogue signals, increasingly telephone service providers are transparently converting the signals to digital for transmission before converting them back to analogue for reception. 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 analogue 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). ^[41] In terms of new subscriptions over the five years from 1999, Africa has outpaced other markets with 58. 2% growth. ^[42] 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 depreciate analogue systems such as AMPS. GSM ( Global System for Mobile communications: originally from Groupe Spécial Mobile) is the most popular standard for Mobile phones in the W-CDMA ( Wideband Code Division Multiple Access) is a type of 3G Cellular network. ^[43]

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 optic fibres. TAT-8 was the 8th Transatlantic telephone cable,initially carrying 40000 telephone circuits (simultaneous calls between USA, England and France An optical fiber (or fibre) is a Glass or Plastic fiber that carries Light along its length The benefit of communicating with optic fibres 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 optic fibre cables are able to carry 25 times as many telephone calls as TAT-8. ^[44] This increase in data capacity is due to several factors: First, optic fibres are physically much smaller than competing technologies. Second, they do not suffer from crosstalk which means several hundred of them can be easily bundled together in a single cable. In Electronics, the term crosstalk ( XT) refers to any phenomenon by which a signal transmitted on one circuit or channel of a Transmission system ^[45] Lastly, improvements in multiplexing have led to an exponential growth in the data capacity of a single fibre. ^[46]^[47]

Assisting communication across many modern optic fibre networks is a protocol known as Asynchronous Transfer Mode (ATM). In electronic digital data transmission systems the Network protocol Asynchronous Transfer Mode (ATM encodes data traffic into small fixed-sized cells 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. If a service (or application wishes to use a broadband network (an ATM network in particular to transport a particular kind of traffic it must first inform the network about 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. ^[48] 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. MPLS redirects here For other uses see Mpls In Computer networking and Telecommunications, Multi Protocol Label Switching ^[49]

Radio and television

Digital television standards and their adoption worldwide.

In a broadcast system, a central high-powered broadcast tower transmits a high-frequency electromagnetic wave to numerous low-powered receivers. Radio masts and towers are typically tall structures designed Electromagnetic radiation takes the form of self-propagating Waves in a Vacuum or in Matter. The high-frequency wave sent by the tower is modulated with a signal containing visual or audio information. In Telecommunications, modulation is the process of varying a periodic Waveform, i The antenna of the receiver is then 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. An antenna is a Transducer designed to transmit or Receive electromagnetic waves In other words antennas convert electromagnetic waves into An antenna tuner, transmatch or antenna tuning unit (ATU matches a transceiver with a fixed impedance (typically 50 Ohms for modern transceivers to a load (feed The broadcast signal can be either analogue (signal is varied continuously with respect to the information) or digital (information is encoded as a set of discrete values). ^[50]^[51]

The broadcast media industry is at a critical turning point in its development, with many countries moving from analogue to digital broadcasts. This move is made possible by the production of cheaper, faster and more capable integrated circuits. Microchipsjpg|right|thumb|200px|Microchips ( EPROM memory with a transparent window showing the integrated circuit inside The chief advantage of digital broadcasts is that they prevent a number of complaints with traditional analogue broadcasts. For television, this includes the elimination of problems such as snowy pictures, ghosting and other distortion. Noise in analog Video and Television is perceived as a random dot pattern which is superimposed on the picture as a result of Electronic noise and See also Television interference In Television, a ghost is an unwanted Image on the screen appearing Superimposed on the desired These occur because of the nature of analogue transmission, which means that perturbations due to noise will be evident in the final output. is a one volume manga created by Tsutomu Nihei as a prequel to his ten-volume work Blame!. 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 Telecommunication and Information theory, forward error correction (FEC is a System of Error control for Data transmission, whereby ^[52]^[53]

In digital television broadcasting, there are three competing standards that are likely to be adopted worldwide. These are the ATSC, DVB and ISDB standards; the adoption of these standards thus far is presented in the captioned map. For the chemical compound see Divinylbenzene. Digital Video Broadcasting ( DVB) is a suite of internationally accepted Integrated Services Digital Broadcasting (ISDB is a Japanese standard for Digital television (DTV and Digital radio used by the country's radio All three standards use MPEG-2 for video compression. MPEG-2 is a standard for "the generic coding of moving pictures and associated audio information" 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. Dolby Digital is the marketing name for a series of lossy audio compression technologies developed by Dolby Advanced Audio Coding ( AAC) is a standardized lossy compression and encoding scheme for Digital audio. MPEG-1 was an early Standard for Lossy compression of Video and audio. ^[54]^[55] 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). Digital Audio Broadcasting ( DAB) also known as Eureka 147, is a Digital radio technology for Broadcasting Radio stations used in Digital Audio Broadcasting ( DAB) also known as Eureka 147, is a Digital radio technology for Broadcasting Radio stations used in The exception being the United States which has chosen to adopt HD Radio. HD Radio is the name used by iBiquity for a system of digital transmission for audio broadcast stations 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 analogue transmissions. In-band on-channel ( IBOC) is a method of transmitting Digital radio and Analog radio broadcast signals simultaneously on ^[56]

However, despite the pending switch to digital, analogue receivers still remain widespread. Analogue television is still transmitted in practically all countries. The United States had hoped to end analogue broadcasts on December 31, 2006; however, this was recently pushed back to February 17, 2009. Events 406 – Vandals, Alans and Suebians cross the Rhine, beginning an invasion of Gallia. Year 2006 ( MMVI) was a Common year starting on Sunday of the Gregorian calendar. Events 1500 - Battle of Hemmingstedt. 1600 - Philosopher Giordano Bruno is burned alive at Campo de' Fiori This article is about the year For the film see 2009 Lost Memories. ^[57] For analogue television, there are three standards in use (see a map on adoption here). These are known as PAL, NTSC and SECAM. PAL, short for Phase Alternating Line, is a colour -encoding system used in Broadcast television systems in large parts of the world NTSC ( National Television System Committee) is the Analog television system used in the United States, Canada, Japan, Mexico SECAM, also written SÉCAM ( Séquentiel couleur à mémoire, French for "Sequential Color with Memory" is an analog color television system For analogue radio, the switch to digital is made more difficult by the fact that analogue receivers are a fraction of the cost of digital receivers. ^[58]^[59] The choice of modulation for analogue radio is typically between amplitude modulation (AM) or frequency modulation (FM). Amplitude modulation ( AM) is a technique used in electronic communication most commonly for transmitting information via a Radio Carrier wave To achieve stereo playback, an amplitude modulated subcarrier is used for stereo FM. Stereophonic sound, commonly called stereo, is the reproduction of Sound, using two or more independent audio channels through a Symmetrical See also Frequency modulation, FM band FM broadcasting is a broadcast Technology invented by Edwin Howard Armstrong that

The Internet

The OSI reference model

The Internet is a worldwide network of computers and computer networks that can communicate with each other using the Internet Protocol. The Open Systems Interconnection Basic Reference Model (OSI Reference Model or OSI Model) is an abstract description for layered communications and computer Network protocol The Internet Protocol ( IP) is a protocol used for communicating data across a Packet-switched Internetwork using the Internet Protocol ^[60] Any computer on the Internet has a unique IP address that can be used by other computers to route information to it. An Internet Protocol ( IP) address is a numerical identification ( Logical address) that is assigned to devices participating in a Computer network 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. In this way, the Internet can be seen as an exchange of messages between computers. ^[61]

An estimated 16. 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 (69. 7%), Oceania/Australia (53. 5%) and Europe (38. 9%). ^[62] In terms of broadband access, Iceland (26. Broadband Internet access, often shortened to just Broadband, is high-speed Internet access—typically contrasted with dial-up access over a Modem Iceland, officially the Republic of Iceland ( ( Ísland or Lýðveldið Ísland ( 7%), South Korea (25. South Korea, officially the Republic of Korea and often referred to as Korea ( Korean: 대한민국 tɛː 4%) and the Netherlands (25. The Netherlands ( Dutch:, ˈnedərlɑnt is the European part of the Kingdom of the Netherlands, which consists of the Netherlands the Netherlands 3%) lead the world. ^[63]

The Internet works in part because of protocols that govern how the computers and routers communicate with each other. In the field of Telecommunications, a communications protocol is the set of standard rules for data representation signaling authentication and error detection required to 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. A web browser is a software application which enables a user to display and interact with text images videos music games and other information typically located on a Ethernet is a family of frame -based Computer networking technologies for Local area networks (LANs Wi-Fi (ˈwaɪfaɪ is the trade name for the popular wireless technology used 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. The Open Systems Interconnection Basic Reference Model (OSI Reference Model or OSI Model) is an abstract description for layered communications and computer Network protocol ^[64]

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 fibre. In electronic digital data transmission systems the Network protocol Asynchronous Transfer Mode (ATM encodes data traffic into small fixed-sized cells This is because for most intercontinental communication the Internet shares the same infrastructure as the public switched telephone network. The public switched telephone network ( PSTN) is the network of the world's public circuit-switched Telephone networks in much the same way that the

At the network layer, things become standardized with the Internet Protocol (IP) being adopted for logical addressing. The Internet Protocol ( IP) is a protocol used for communicating data across a Packet-switched Internetwork using the Internet Protocol In Data Networks In computer networks a logical address refers to a Network layer address such as an IP 192 For the world wide web, these “IP addresses” are derived from the human readable form using the Domain Name System (e. The Domain Name System (DNS is a hierarchical naming system for computers services or any resource participating in the Internet. 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. ^[65]

At the transport layer, most communication adopts either the Transmission Control Protocol (TCP) or the User Datagram Protocol (UDP). The Transmission Control Protocol (TCP is one of the core protocols of the Internet Protocol Suite. User Datagram Protocol ( UDP) is one of the core protocols of the Internet Protocol Suite. TCP is used when it is essential every message sent is received by the other computer where as 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 or retransmitted if lost. Both TCP and UDP packets carry port numbers with them to specify what application or process the packet should be handled by. In Computer networking, a port is an application-specific or process-specific software construct serving as a communications endpoint used by Transport Layer protocols In computing a process is an instance of a Computer program that is being sequentially executed by a computer system that has the ability to run several computer ^[66] Because certain application-level protocols use certain ports, network administrators can restrict Internet access by blocking the traffic destined for a particular port. The Transmission Control Protocol ( TCP) and the User Datagram Protocol ( UDP) are Transport Layer protocols of the Internet Protocol

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. Transport Layer Security ( TLS) and its predecessor Secure Sockets Layer ( SSL) are Cryptographic protocols that provide secure Transport Layer Security ( TLS) and its predecessor Secure Sockets Layer ( SSL) are Cryptographic protocols that provide secure These protocols ensure that the data transferred between two parties remains completely confidential and one or the other is in use when a padlock appears at the bottom of your web browser. ^[67] Finally, at the application layer, are many of the protocols Internet users would be familiar with such as HTTP (web browsing), POP3 (e-mail), FTP (file transfer), IRC (Internet chat), BitTorrent (file sharing) and OSCAR (instant messaging). Hypertext Transfer Protocol ( HTTP) is a Communications protocol for the transfer of information on the Internet. In Computing, local E-mail clients use the Post Office Protocol version 3 ( POP3) an application-layer Internet standard protocol BitTorrent is a Peer-to-peer File sharing protocol used to distribute large amounts of Data. OSCAR is AOL 's flagship Instant messaging and Presence information protocol standing for O pen S ystem for C ommunic'

Local area networks

Despite the growth of the Internet, the characteristics of local area networks (computer networks that run at most a few kilometres) 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.

In the mid-1980s, several protocol suites emerged to fill the gap between the data link and applications layer of the OSI reference model. The Open Systems Interconnection Basic Reference Model (OSI Reference Model or OSI Model) is an abstract description for layered communications and computer Network protocol These were Appletalk, IPX and NetBIOS with the dominant protocol suite during the early 1990s being IPX due to its popularity with MS-DOS users. AppleTalk is a proprietary suite of protocols developed by Apple Inc for networking computers Internetwork Packet Exchange ( IPX) is the OSI-model Network layer protocol in the IPX/SPX Protocol stack. NetBIOS ( is an acronym for Network Basic Input/Output System. MS-DOS (short for M icro' s' oft D isk O perating S ystem is an Operating system commercialized by Microsoft. TCP/IP existed at this point but was typically only used by large government and research facilities. The Internet Protocol Suite (commonly TCP/IP) is the set of Communications protocols used for the Internet and other similar networks ^[68] As the Internet grew in popularity and a larger percentage of traffic became Internet-related, local area networks gradually moved towards TCP/IP and today networks mostly dedicated to TCP/IP traffic are common. The move to TCP/IP was helped by technologies such as DHCP that allowed TCP/IP clients to discover their own network address — a functionality that came standard with the AppleTalk/IPX/NetBIOS protocol suites. ^[69]

It is at the data link layer though that most modern local area networks diverge from the Internet. Whereas Asynchronous Transfer Mode (ATM) or Multiprotocol Label Switching (MPLS) are typical data link protocols for larger networks, Ethernet and Token Ring are typical data link protocols for local area networks. In electronic digital data transmission systems the Network protocol Asynchronous Transfer Mode (ATM encodes data traffic into small fixed-sized cells MPLS redirects here For other uses see Mpls In Computer networking and Telecommunications, Multi Protocol Label Switching Ethernet is a family of frame -based Computer networking technologies for Local area networks (LANs Token ring Local area network (LAN technology is a local area network protocol which resides at the Data link layer 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 collision prevention. Carrier Sense Multiple Access With Collision Detection ( CSMA/CD) in Computer networking is a network control protocol in which a Both of these differences allow for more economic set-ups. ^[70]

Despite the modest popularity of Token Ring in the 80's and 90's, virtually all local area networks now use wired or wireless Ethernet. Token ring Local area network (LAN technology is a local area network protocol which resides at the Data link layer Ethernet is a family of frame -based Computer networking technologies for Local area networks (LANs At the physical layer, most wired Ethernet implementations use copper twisted-pair cables (including the common 10BASE-T networks). Twisted pair Cabling is a form of wiring in which two conductors (two halves of a single circuit) are wound together for the purposes of canceling out However, some early implementations used coaxial cables and some recent implementations (especially high-speed ones) use optic fibres. Coaxial cable is a cable consisting of an inner conductor surrounded by a tubular insulating layer typically made from a flexible material with a high Dielectric constant, all An optical fiber (or fibre) is a Glass or Plastic fiber that carries Light along its length Optic fibres are also likely to feature prominently in the forthcoming 10-gigabit Ethernet implementations. ^[71] Where optic fibre is used, the distinction must be made between multi-mode fibre and single-mode fibre. Multi-mode fibre can be thought of as thicker optical fibre that is cheaper to manufacture but that suffers from less usable bandwidth and greater attenuation (i. Multi-mode optical fiber ( multimode fiber or MM fiber or fibre) is a type of Optical fiber mostly used for communication over shorter distances e. poor long-distance performance). ^[72]