Alexander Graham Bell

Telecommunications is defined as the remote transmission of information with basic means of electronic and information technology. This term has a broader meaning than its equivalent official " electronic communication ". They are thus distinguished from the station that transmits information or objects in physical form.

In the early days of modern telecommunications, inventors like Antonio Meucci , Alexander Graham Bell and Guglielmo Marconi developed communication devices as the telegraph , the telephone or radio. They have revolutionized the traditional means such as flags or optical telegraph Chappe.

Currently, telecommunications generally involve the use of electronic equipment associated with networks such as analog or digital phone or mobile, radio, television or computer. They are also an important part of the economy and are subject to global regulations.

Etymology

The word comes from the Greek prefix telecommunications tele-(-), meaning far, and Latin communicare, meaning share .

Definition

Telecommunications Telecoms) are considered as technologies and techniques applied, not a science.

Telecommunications means any transmission , emission and reception at a distance, signs of signals , writing, with pictures , of sounds or intelligence of any nature by wire , radio technology , connection optical , or other systems electromagnetic .

History

Origin of telecommunications

The former natural means simple as speech or visual signals, can communicate over short distances. The need to communicate at greater distances in human societies organized quickly brought to expand telecommunications primitive drums , smoke signals , whistling language , etc. ..

Some of these types of communications, such as flags , semaphores or heliographs are still used in the Navy, although this usage has become marginal.

Telegraph and telephone

The phone of Alexander Graham Bell at the Museum of Arts and Crafts in Paris.

Although the optical signal communication between the high points is very old, it owes to the engineer Claude Chappe creation from 1794 of the first network simple and efficient optical transmission of messages. The network he has called "telegraph" was developed on the main French and remained in service until 1848.

The first commercial telegraph electric was built by Charles Wheatstone and William Fothergill Cooke and opened in 1839. Was improved electromagnetic telegraph already invented . Samuel Morse independently developed a version of the electric telegraph, he showed September 2, 1837. The Morse code was a major advance on the Wheatstone telegraph.

The first transatlantic telegraph cable was completed on 27 July 1866 . Its length was 4200 km for a total weight of 7000 tons.

The telephone was invented independently by classical Alexander Bell and Elisha Gray in 1876. However, it is Antonio Meucci invented the first device capable of transmitting voice with a line crossed by a signal.

Science and Telecommunications

Telecommunications is a place of convergence and interaction between different technologies and scientific disciplines about it revolutionized the world of distance communication through the development of programming languages and computer programs ( software engineering ) associated with microelectronics.

Technical Telecommunications

Principles

A telecommunications link comprises three main elements:

• a transmitter that takes information and converts it into an electrical signal, optical or radio;
• a transmission medium, may be a transmission line , a fiber optic or radio space, which connects the transmitter and receiver;
• a receiver that receives the signal and converts it into usable information.

For example, broadcasting, broadcasting transmitter through its antenna emits voice or music, which goes into space as electromagnetic waves to a receiver AM or FM who will return.

Communication links can be unidirectional, as in radio or television, or bi, then using a transceiver. When several links are interconnected with multiple users, one obtains a network , such as the telephone network or Internet.

Transmission media

Optical fibers.

Transmission occurs through different media in different systems. Historically the telephone line was the first telecommunications carrier and allowed the development of the telegraph and telephone. He is still the main medium for connecting networks and telephone networks (telephone, fax, Minitel, Internet, ...), as a pair (s) twisted (s).

The coaxial cable was broadband media before the advent of fiber optics, it is still used in industrial networks due to its robustness against disturbances. It is also the preferred medium for radio frequency connections within a device, sometimes replaced by the waveguide for transmission of microwave high power.

The optical fiber that connects progressively subscribers in the city, is also the medium of submarine cable modern. It's a wire in glass or plastic that has very fine property to conduct the light.

"Radio", which can be defined as any communication via the airwaves, has revolutionized telecommunications in the early ^twentieth century. This is the medium of broadcasting programs, services, communications radio , networks, mobile telephony , the Wi-Fi , leisure radio as ham radio , links via satellite communications or microwave , as well as simple remote home. The radio engineering studies the transmission of radio waves, the wave propagation , interfaces with the transmitter and receiver via antenna.

Optical links in space, so they are not guided by fibers are used in satellite communications, as well as in applications as simple as remote audio-video.

Lastly, some environments can be traversed only by acoustic waves, in the case of communications in mines, or between divers, which is by ultrasonic waves.

Transmission and Reception

HF antenna curtain telecommunications.

Whatever the transmission medium, a transmitter converts the information into an electrical signal, optical or radio adapted to the media, by modulating and amplifying it. Conversely, a receiver converts the signal into usable information.

The technique of these interface functions is highly dependent on the media, frequency of use, and especially the power required to compensate for propagation losses. Thus, the transmission line Ethernet example uses only a few integrated circuits and cable of small diameter, while a connection to a probe global demand high power transmitters and antennas of several tens of meters.

In a wireless transmission channel, the signal carried by the radio wave is attenuated by the loss of space, atmospheric absorption and precipitation, and degraded by diffraction and reflection. The Equation of telecommunications includes all these factors and determines the power and antennas needed.

The radio antenna converts electrical signals into radio waves to the issue, and vice versa for reception. Many types of antennas have been developed, by frequency of use, the necessary gain and application, from miniature antennas embedded in mobile phones, to the parables of giant radio astronomy.

In bidirectional applications, such as radio, the two functions can be combined into a transceiver. Receiver followed by a transmitter is a repeater , for example on a telecommunications satellite , cable or a submarine.

Sharing of transmission media

The sharing of media between users is through the allocation techniques, multiplexing and multiple access.

The assignment of frequencies per band and per service on the media airwaves is the first technique appeared to prevent mutual interference.

Within a band of frequencies, the frequency multiplexing is the division of a transmission medium into multiple channels, each assigned to a link. This assignment can be fixed, for example by broadcasting FM , a station broadcasts at 96.1 MHz, another at 94.5 MHz. The assignment of frequencies can be dynamic as in FDMA (multiple access frequency division), used for example in satellite transmissions. Each user will receive the channel in this case a temporary permission for one of the available frequencies.

In digital communications, multiplexing can also be time or code :

• The techniques of spread spectrum such as ( CDMA ) are used particularly in mobile telephony. Each association is modulated by a unique spreading code, for which the other users appear as noise after demodulation.
• The encoding packets ( TDMA ) system is the key to ATM and international communications across the Internet. Each user will transmit "digital packets" provided with addresses that were repeated in the channel.

The operation of these techniques require multiple access protocols for requests for assignment, addressing, the best known is the TCP / IP Internet.

Signal

The signal processing can tailor the information (in the form of analog or digital) to the transmission medium and the return receipt.

Upon issuance, the techniques of compression to reduce the flow required, ideally without noticeable loss of quality, such as music ( MP3 ) or video ( MPEG ), the coding process the information signal into a binary form suitable for modulation.

Upon receipt, the inverse operations are performed: demodulation, decoding, decompression and correction. The error correction can, thanks to the addition of redundant information by a correction code to divide by several orders of magnitude the error rate.

These techniques vary depending on whether the signals transmitted are analog, such as music, voice, image, or digital, such as files or text. An analog signal varies continuously when a signal digital is a succession of discrete, binary in the simplest case, succeeding in sequence.

In many applications ( TNT , mobile, etc.), the analog signal is converted to digital , enabling more effective treatment, particularly filtering noise . Only the modulation, amplification and coupling to the media while still analog.

Systems and Networks

A set of links and features to provide a service, is a system of telecommunications.

Thus the system of satellites Inmarsat , designed for mobile communications, has several satellites, several types of links to users based on usage rates and thousands of terminals adapted, and links to remote telemetry and control of satellites from the ground stations, they are also connected by dedicated terrestrial links.

A telecommunications system may have an architecture:

Visualization of multiple paths through a portion of the Internet.

• type "point to point", such as a cable radio, optical or radio-telephone. Of repeaters can be included to amplify the signals and correct;
• "dissemination", as in television, where a transmitter is received by thousands of receivers;
• "collection", as oceanographic monitoring, where hundreds of sensors are received by a central system;
• in structure of network , where a set of transmitters and receivers communicate with each other by links "stellate" ( topology star) or "point to point. It is the most common.

An emergency radio network is a simple network between a central and mobiles, run by radio procedures and operators.

A switched network like the telephone network includes individual subscriber connections as an analog line or a line ISDN , the telephone exchanges to establish a circuit between two subscribers and broadband connections to link exchanges.

A packet network, such as Internet , includes routers which direct packets of information from one machine to another designated by its IP address.

Applications of Telecommunications

Voice and Sound

Wired telephone recently.

Transporting voice over the telephone , was the first advance of telecommunications, just after the first telegraph. The phone is the device used to hold a two-way conversation with a distant person. It is used for private purposes, to keep in touch with loved ones or professionally, to exchange information orally without having to meet physically.

Telephony based on the telephone network also enables more advanced services such as voicemail, conference calling and voice services. The telephone line is also the Internet access solution, first with a modem on dial and broadband through the ADSL.

The radio , that is to say, the remote wireless communication, was first applied to marine communications to increase security and military from World War before becoming a media popular with the TSF. The radio is still the primary means of communication from air traffic control , maritime links with the marine radio links and security (police, emergency). It is also the main activity of the ham radio.

The Broadcasting is the distribution of programs from a transmitter to auditors equipped with a receiver. First, by amplitude modulation by low frequency (LW) and medium frequency (MW), then FM in VHF , it evolves into the digital radio broadcast satellite or terrestrial VHF.

The mobile phone is the ability to wirelessly or through a solution based on terrestrial coverage areas, relay or satellite. The development of this medium is a remarkable social phenomenon of the late ^twentieth century. The gesture of calling in the street becomes commonplace, so much worry about its health hazards and create a special language, the language SMS. Access to the Internet and television is already easy with the latest generation of phones.

Image and video

The transmission of images back to dial- Facsimile , and is still used under the abbreviated name of fax , as an exchange of photocopied pages, business documents or art. The RADIOFACSIMILE that transmits images via radio is used primarily for distributing weather maps, either directly from Earth observation satellites, is relayed to the ships or airfields.

UHF TV antennas

After the telephone and radio, television is present in every household. Forests of antennas yagi and parables have invaded the towns, satellite tv, digital and analog first multiplied the national and international programs.

Receptors modern plasma or LCD provides high quality images and digital terrestrial TV will expand the choice of users.

The simultaneous transmission of images to a telephone connection is possible thanks to the videoconferencing using broadband channel dedicated for transmission or slow-scan analog SSTV , immortalized by the first steps on the moon, and the new digital technology , webcam on Internet or mobile phone next generation.

Preparation and Presentation, Oct. 29, 2001, the first transmission of digital cinema via satellite in Europe of a feature film by Bernard Pauchon Alain Lorentz, Melwig Raymond, Philippe Dinant.

Text and data

The telegraph was the ancestor of data transmissions and the first application of telecommunications: transmitting characters, so a message, for optical signals, then a line then by radio waves ( wireless telegraphy ). The teletype then radioteletypewriter have automated.

A computer network is a set of equipment linked together to exchange information. Although the Internet is not the only computer network system, it has almost become synonymous. The Internet structure is complex and can be separated into several parts:

• communication functions (lines subscribers, modems , and routers that connect to the Web);
• transport functions between users (the protocols , the servers ,...);
• applications that provide the final service ( mail , image, voice, search , etc.).

The telemetry , land as hydrology or meteorology, or space such as images Meteosat or those of distant planetary probes, allows the monitoring of industrial facilities, increase our knowledge of the environment, climate or the universe.

The remote , as the easiest home automation or HiFi, video, or more complex like the Mars rovers, the remote control is wireless, optical or radio, usually coupled with telemetry.

Other applications

The radio signal may contain other information such as parameters for the calculation of position, universal time, target detection and terrain mapping.

This antenna long range radar is known as ALTAIR. It is located on the atoll of Kwajalein Marshall Islands.

Although the radar is not strictly a communication system, but remote sensing, techniques combine microwave, signal processing, radio, and can be attached to the world of telecommunications.

Originally developed for the detection of air raids, the radar was quickly installed on ships and airplanes.

First military and civilian air traffic control and maritime use radar extensively for safety. Finally the weather radar can map the rain and clouds, including from satellite observation.

Three GPS receivers

The navigation has enabled the early days of radio, to assist in the shipping and aviation, through the direction finding and radio beacons , then the hyperbolic systems such as LORAN. The satellite navigation systems such as a href = "Global_Positioning_System" title = "Global Positioning System> GPS has become a standard equipment of vehicles, pending the development of future Galileo.

The automatic identification systems such as AIS and obstacle detection improve navigation safety.

The spread of universal time and time signal is integrated with GPS navigation signals today, but has long been a service-specific navigation aid astronomical, scientific or synchronization by RF emissions as WWV , or BF as the transmitter Allouis or DCF77.

For telecommunications, military use methods of secrecy as frequency hopping and encryption , networks of HF and VHF radio, satellite or dedicated, as Syracuse. Governments also use radio techniques in signals intelligence purposes, as the system Echelon listening satellite ^{Telecommunications and Society}

Telecommunications is a sector of economic activity significantly.

Telecommunications and Development

A large call center located in Lakeland , in Florida.

Telecommunications are a crucial element of modern society. In 2006, the telecommunications industry accounted for an income of 1 200 billion, representing 3% of world income .

At the microeconomic level, companies are using telecommunications to build their business, as online sales, or improve their effectiveness as traditional stores . In the world of home care services can be obtained on telephone call, delivering pizzas to troubleshooting. In poorer communities, the mobile phone is used both in Bangladesh than in Cte d'Ivoire to negotiate agricultural sales to the best market price .

Because of the economic benefits of a proper infrastructure for telecommunications, on which much of the world has no access, the development gap through lack of telecommunications, or digital divide may widen .

Culture and Telecommunications

Modern telecommunications can transmit the image, sound and text worldwide. These technologies are neutral with respect to their content. However, telecommunications are the source of debate in terms of standardization of culture, national identity or, conversely, new possibilities of expression, communication to overcome the traditional boundaries and spaces.

The development of means of microwave transmission, land and satellite, has fostered the widespread deployment of mass media (radio, television ...) in companies , changing modes of thought and traditional cultural patterns. For example, during the Cold War radio received international shortwave transmitters from the U.S. to the GDR , from Russia to Europe or China installed in Albania , has served as media propaganda between two ideologies. Satellite television with satellite dishes adorn the buildings of the European suburbs, allows minority communities keep their cultural ties.

Finally, the convergence of digital networks and telecommunications infrastructure worldwide can connect to the Web through the network Internet almost anywhere on the earth's surface. This new mode of communication is gradually transforming the ways to exchange, communicate and work not only in a society but also between companies from different cultures.

However, there are also web albums such as CDs and movies before they are sold, causing reactions restrictive or police, major distributors. The true or false information can move in a few days, extremist or criminal groups can organize themselves without limitation.

Business Telecommunications

The industrial design and produce telecommunications equipment and software for telecommunications. They also participate in standardization by proposing new solutions to standards bodies.

The builders may be enterprises multinationals from several mergers and acquisitions as Aastra , Alcatel-Lucent , Nokia-Siemens , or startups like Fortinet. They are mainly from North America: Cisco , 3Com , Nortel , Europe: Alcatel-Lucent , Ericsson , Nokia and China (ROC or PRC): Huawei , ZTE , D-Link.

Some manufacturers focus on technology as Extreme Networks on the Ethernet. Others, like Cisco , are trying to cover all technologies, all markets (individual, company, telecom operator), all services (support, installation, architecture, etc.).

A telecommunications operator is a company that sells services using telecommunications infrastructure. This may be an independent company or a subsidiary of a manufacturer that leases capacity on a network to sell subscriptions and individual connections, or property owner of a public network, such as incumbents in Europe.

Organizations and standardization

The interoperability between different systems or equipment required standards and protocols of telecommunications specific versions that evolve by successive technical advances. A manufacturer with one or more innovations are the basis of a norm or standard, is sure to make a significant advance in its market, equipment manufacturers weave so very close links with standards bodies and standardization.

Among the leading standards-global standardization include:

• the ETSI : European Telecommunications Standards Institute or Institute European Telecommunications Standards;
• the ITU : International Telecommunication Union or the International Telecommunication Union;
• the IETF : Internet Engineering Task Force;
• the ATM Forum ;
• the ANSI : American National Standards Institute;
• the IEEE : Institute of Electrical and Electronics Engineers.

Telecommunications Authority

To optimize the use of frequency spectrum and minimize interference between systems, states agree on an international level:

• in Europe by the CEPT ( European Conference of Postal and Telecommunications );
• internationally by the ITU - International Telecommunication Union (UN agency);
• by revisions of the "Radio Regulations" or RR are provided within the WRC (World Radiocommunication Conference) or WRC (World Radiocommunication Conference).

Each country manages those international regulations within its borders, under the control of national governments:

• the FCC (Federal Communications Commission of) the United States;
• the ARCEP (regulatory authority for electronic communications and postal services) and ANFR (National Frequencies Agency), France;

The telecommunications sector was historically linked to the sovereign authority of each state and operated by this state. From 1980-1990, a worldwide movement of de-regulation (or de-regulation) of the telecommunications sector is reached, leading by example in unbundling of the telephone network.

Telecommunications and the Environment

According to research firm Gartner, in 2009, the telecommunications and information would be responsible for 2% of anthropogenic emissions of greenhouse gases (equivalent to aviation)

See also

Related articles

• Computer Law
• Telecommunications Law
• ICANN
• Health risks of telecommunications

External Links

• Regulatory authority for electronic communications , ARCEP , France
• Site Service Technology and Information Society (STSI), Ministry of Economy, Industry and Employment , France

Bibliography

• (En) A Global History Of The Mobile Phone. Constant Touch (Totem Books - 2004) ( ISBN 1840465417 )
• (With) City of Light, The Story of Fiber Optics. Jeff Hecht (Oxford University Press, New York - 1999) ( ISBN 0-19-510818-3 )
• Encyclopedia of Posts, Telegraphs and Telephones. 2 volumes (Rombaldi - 1957) (417 and 426 pages)
• Globalstar constellation of 48 satellites for mobile phone. Guy Lebgue in ( Aerospace Review , No. 115 - February 1995)
• (In) Inventing the Internet. Janet Abbate (Cambridge, Mass.. MIT Press - 1999) (268 pages) ( ISBN 978-0262011723 )
• Radar, 1904-2004. History of a century of technical innovation and operational. Yves Blanchard. (Editions Ellipses - 2004) ( ISBN 2729818022 )
• Computer Networks: Fundamentals. Standards, Architecture, OSI Model, TCP / IP, Ethernet, Wi-Fi ... Atelin Philip Jos Dordoigne (ENI - 2006) (452 pages) ( ISBN 978-2746031548 )
• Networking and Telecommunications. Claude Servin (Ed. Dunod. Collection Sciences Sup - 2006) (940 pages) ( ISBN 2-10-049148-2 )

References

• Telecommunication Portal
• Portal electricity and electronics

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