99-415: The Pontop Pike transmitting station is a facility for telecommunications and broadcasting situated on a 312-metre (1,024-ft) high hill of the same name between Stanley and Consett , County Durham, near the village of Dipton , England. The mast is 149 metres (489 ft) high, giving an average antenna height of 461 metres (1,512 ft) above sea level. It is owned and operated by Arqiva . The mast
198-412: A thermionic tube or thermionic valve uses thermionic emission of electrons from a heated cathode for a number of fundamental electronic functions such as signal amplification and current rectification . The simplest vacuum tube, the diode invented in 1904 by John Ambrose Fleming , contains only a heated electron-emitting cathode and an anode. Electrons can only flow in one direction through
297-411: A radio broadcasting station , the station's large power amplifier is the transmitter and the broadcasting 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, where it
396-411: A better price for their goods. In Côte d'Ivoire , coffee growers share mobile phones to follow hourly variations in coffee prices and sell at the best price. On the 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
495-438: A caveat for it in 1876. Gray abandoned his caveat and because he did not contest Bell's priority, the examiner approved Bell's patent on March 3, 1876. Gray had filed his caveat for the variable resistance telephone, but Bell was the first to document the idea and test it in a telephone.[88] Antonio Meucci invented a device that allowed the electrical transmission of voice over a line nearly 30 years before in 1849, but his device
594-441: 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. Another advantage of digital systems over analogue is that their output is easier to store in memory, i.e., two voltage states (high and low) are easier to store than
693-495: A continuous range of states. 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 per cent of the gross world product (official exchange rate). Several following sections discuss the impact of telecommunication on society. On the microeconomic scale, companies have used telecommunications to help build global business empires. This
792-456: A heliograph depends on the opacity of the air and the effective collecting area of the mirrors. Heliograph mirrors ranged from 1.5 to 12 in (38 to 305 mm) or more. Stations at higher altitudes benefit from thinner, clearer air, and are required in any event for great ranges, to clear the curvature of the Earth . A good approximation for ranges of 20 to 50 mi (32 to 80 km) is that
891-406: 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
990-450: A key advantage of digital signals over analogue signals. However, digital systems fail catastrophically when noise exceeds the system's ability to autocorrect. On the other hand, analogue systems fail gracefully: as noise increases, the signal becomes progressively more degraded but still usable. Also, digital transmission of continuous data unavoidably adds quantization noise to the output. This can be reduced, but not eliminated, only at
1089-838: 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
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#17327977399141188-437: 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
1287-491: A radio as the channel "96 FM"). In addition, modulation has the advantage that it may use frequency division multiplexing (FDM). 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 routers that work together to transmit information to the correct user. An analogue communications network consists of one or more switches that establish
1386-539: A range of 35 mi (56 km) with favorable results. During the Jowaki Afridi expedition sent by the British-Indian government in 1877, the heliograph was first tested in war. The simple and effective instrument that Mance invented was to be an important part of military communications for more than 60 years. The usefulness of heliographs was limited to daytimes with strong sunlight, but they were
1485-632: A rugged and broken country, which was the stronghold of the Apache , Commanche and other hostile native Indian tribes. By 1887, heliographs in use included not only the British Mance and Begbie heliographs, but also the American Grugan, Garner and Pursell heliographs. The Grugan and Pursell heliographs used shutters, and the others used movable mirrors operated by a finger key. The Mance, Grugan and Pursell heliographs used two tripods, and
1584-475: A service that operated for a year until the gap in the telegraph link was closed. In the Middle Ages, chains of beacons were commonly used on hilltops as a means of relaying a signal. Beacon chains suffered the drawback that they could only pass a single bit of information, so the meaning of the message such as "the enemy has been sighted" had to be agreed upon in advance. One notable instance of their use
1683-442: A single medium to transmit several concurrent communication sessions . Several methods of long-distance communication before the modern era used sounds like coded drumbeats , the blowing of horns , and whistles . Long-distance technologies invented during the 20th and 21st centuries generally use electric power, and include the telegraph , telephone , television , and radio . Early telecommunication networks used metal wires as
1782-411: 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 dials the number. Once the connection is made, the caller's voice is transformed to an electrical signal using a small microphone in
1881-693: A total cost of $ 4,205. By 1893, the number of heliographs manufactured for the American Army Signal Corps was 133. The heyday of the heliograph was probably the Second Boer War of the 1890s and early 1900s in South Africa, where it was much used by both the British and the native immigrant Boers . The terrain and climate, as well as the nature of the campaign, made heliography a logical choice. For night communications,
1980-412: A version of the electrical telegraph that he unsuccessfully demonstrated on September 2, 1837. His code was an important advance over Wheatstone's signaling method. The first transatlantic telegraph cable was successfully completed on July 27, 1866, allowing transatlantic telecommunication for the first time. The conventional telephone was patented by Alexander Bell in 1876. Elisha Gray also filed
2079-581: 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 communication), 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". At
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#17327977399142178-671: Is called point-to-point communication because it occurs between a transmitter and a receiver. Telecommunication through radio broadcasts is called broadcast communication because it occurs between a powerful transmitter and numerous low-power but sensitive radio receivers. Telecommunications in which multiple transmitters and multiple receivers have been designed to cooperate and share the same physical channel are called multiplex systems . The sharing of physical channels using multiplexing often results in significant cost reduction. Multiplexed systems are laid out in telecommunication networks and multiplexed signals are switched at nodes through to
2277-451: 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 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 impressed into
2376-434: Is commonly called "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
2475-794: Is converted from electricity to sound. Telecommunication systems are occasionally "duplex" (two-way systems) with a single box of electronics working as both the transmitter and a receiver, or a transceiver (e.g., a mobile phone ). The transmission electronics and the receiver electronics within a transceiver are quite independent of one another. This can be 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 measured in 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 to avoid interference. Telecommunication over fixed lines
2574-481: Is degraded by undesirable noise . Commonly, the noise in a communication system can be expressed as adding or subtracting from the desirable signal via a random process . This form of noise is called additive noise , with the understanding that the noise can be negative or positive at different instances. Unless the additive noise disturbance exceeds a certain threshold, the information contained in digital signals will remain intact. Their resistance to noise represents
2673-592: Is little evidence that "heliograph" here is other than a misspelling of " holograph ". The term "heliograph" for solar telegraphy did not enter the English language until the 1870s—even the word " telegraphy " was not coined until the 1790s. Henry Christopher Mance (1840–1926), of the British Government's Persian Gulf Telegraph Department, developed the first widely accepted heliograph about 1869, while stationed at Karachi (now in modern Pakistan ) in
2772-609: 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
2871-448: 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 frequencies , and each channel is assigned a separate frequency bandwidth in which to broadcast radio waves. This system of dividing
2970-449: 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 $ 4.7 trillion sector in 2012. The service revenue of the global telecommunications industry was estimated to be $ 1.5 trillion in 2010, corresponding to 2.4% of
3069-569: Is the transmission of information with an immediacy comparable to face-to-face communication. As such, slow communications technologies like postal mail and pneumatic tubes are excluded from the definition. Many transmission media have been used for telecommunications throughout history, from smoke signals , beacons , semaphore telegraphs , signal flags , and optical heliographs to wires and empty space made to carry electromagnetic signals. These paths of transmission may be divided into communication channels for multiplexing , allowing for
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3168-773: The Nipkow disk by Paul Nipkow and thus became known as the mechanical television . It formed the basis of experimental broadcasts done by the British Broadcasting Corporation beginning on 30 September 1929. However, for most of the 20th century, televisions depended on the cathode ray tube invented by Karl Ferdinand Braun . The first version of such a television to show promise was produced by Philo Farnsworth and demonstrated to his family on 7 September 1927. After World War II, interrupted experiments resumed and television became an important home entertainment broadcast medium. The type of device known as
3267-453: The Second Boer War (1899–1902) in South Africa, where both sides used heliographs, tubes were sometimes used to decrease the dispersion of the beam. In some other circumstances, though, a narrow beam made it difficult to stay aligned with a moving target, as when communicating from shore to a moving ship, so the British issued a dispersing lens to broaden the heliograph beam from its natural diameter of 0.5 degrees to 15 degrees. The range of
3366-609: The United States Air Force was working on a space heliograph to signal between satellites In May 2012, "Solar Beacon" robotic mirrors designed at the University of California at Berkeley were mounted on the twin towers of the Golden Gate Bridge at the entrance to San Francisco Bay , and a web site set up where the public could schedule times for the mirrors to signal with sun-flashes, entering
3465-440: The University of Göttingen developed and used a predecessor of the heliograph (the heliotrope ) in 1821. His device directed a controlled beam of sunlight to a distant station to be used as a marker for geodetic survey work, and was suggested as a means of telegraphic communications. This is the first reliably documented heliographic device, despite much speculation about possible ancient incidents of sun-flash signalling, and
3564-440: The spark gap transmitter for radio or mechanical computers for computing, it was the invention of the thermionic vacuum tube that made these technologies widespread and practical, leading to the creation of electronics . In the 1940s, the invention of semiconductor devices made it possible to produce solid-state devices, which are smaller, cheaper, and more efficient, reliable, and durable than thermionic tubes. Starting in
3663-410: The 1840s) reflected by a mirror . The flashes are produced by momentarily pivoting the mirror, or by interrupting the beam with a shutter. The heliograph was a simple but effective instrument for instantaneous optical communication over long distances during the late 19th and early 20th centuries. Its main uses were military, surveying and forest protection work. Heliographs were standard issue in
3762-705: The 1932 Plenipotentiary Telegraph Conference and the International Radiotelegraph Conference in Madrid, the two organizations merged to form the International Telecommunication Union (ITU). They defined telecommunication as "any telegraphic or telephonic communication of signs, signals, writing, facsimiles and sounds of any kind, by wire, wireless or other systems or processes of electric signaling or visual signaling (semaphores)." The definition
3861-497: The 1970s. In the 1960s, Paul Baran and, independently, Donald Davies started to investigate packet switching , a technology that sends a message in portions to its destination asynchronously without passing it through a centralized mainframe . A four-node 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
3960-509: The 19th and 20th centuries were completely manual. The steps of aligning the heliograph on the target, co-aligning the reflected sunbeam with the heliograph, maintaining the sunbeam alignment as the sun moved, transcribing the message into flashes, modulating the sunbeam into those flashes, detecting the flashes at the receiving end, and transcribing the flashes into the message were all done manually. One notable exception – many French heliographs used clockwork heliostats to automatically steer out
4059-559: The British and Royal Australian armies until the 1960s, and were used by the Pakistani army as late as 1975. There were many heliograph types. Most heliographs were variants of the British Army Mance Mark V version (Fig.1). It used a flat round mirror with a small unsilvered spot in the centre. The sender aligned the heliograph to the target by looking at the reflected target in the mirror and moving their head until
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4158-593: The British used some large Aldis lamps , brought inland on railroad cars, and equipped with leaf-type shutters for keying a beam of light into dots and dashes. During the early stages of the war, the British Army garrisons were besieged in Kimberley , along with the sieges of Ladysmith , and at Mafeking . With land wire telegraph lines cut, the only contact with the outside world was via light-beam communication, helio by day, and Aldis lamps at night. In 1909,
4257-466: 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 Niger , Burkina Faso and Mali received the lowest. Telecommunication has played a significant role in social relationships. Nevertheless, devices like
4356-744: 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 laboratories , such as the local area network (LAN) developments of Ethernet (1983), Token Ring (1984) and Star network topology. 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 to 65 EB in 2007. This
4455-538: The U.S. Army demonstrated in the Arizona and New Mexico territories, the possibility of performing communication by heliograph over a heliograph network aggregating 2,000 mi (3,200 km) in length. The network of communication begun by General Miles in 1886, and continued by unsung and now unfortunately relatively unknown Lieutenant W. A. Glassford, was perfected in 1889 at ranges of 85, 88, 95 and 125 mi (137, 142, 153 and 201 km) over
4554-576: The U.S. Forestry Service invented a very portable (4.5 lb [2.0 kg]) heliograph of the single-tripod, shutter plus mirror type for forestry use. Immediately prior to the outbreak of World War I (1914–1918), the mounted cavalry regiments of the Russian Imperial Army in the Russian Empire were still being trained in heliograph communications to augment the efficiency of their scouting and reporting roles. Following
4653-506: The United Kingdom had used the service to coordinate social arrangements and 42% to flirt. 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
4752-797: The United States was spent on media that depend upon telecommunication. 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
4851-466: 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 speaker in that person's handset. Heliograph A heliograph (from Ancient Greek ἥλιος ( hḗlios ) 'sun' and γράφειν ( gráphein ) 'to write') is a solar telegraph system that signals by flashes of sunlight (generally using Morse code from
4950-605: The cities of Newcastle , Durham and Sunderland . It also carries the national BBC Radio FM signals, covering the whole North East , as well as 95.4 MHz FM BBC Newcastle . It was one of the first national FM transmitters in December 1955. All of its television output is within the C/D aerial group. Analogue TV transmissions from this mast began to close from 12 September 2012 and completely ceased on 26 September that year, making Pontop Pike, alongside Bilsdale and Chatton ,
5049-437: The correct destination terminal receiver. Communications can be encoded as analogue or digital signals , which may in turn be carried by analogue or digital communication systems. Analogue signals vary continuously with respect to the information, while digital signals encode information as a set of discrete values (e.g., a set of ones and zeroes). During propagation and reception, information contained in analogue signals
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#17327977399145148-519: The development of optical fibre. The Internet , a technology independent of any given medium, has provided global access to services for individual users and further reduced location and time limitations on communications. Telecommunication is a compound noun of the Greek prefix tele- (τῆλε), meaning distant , far off , or afar , and the Latin verb communicare , meaning to share . Its modern use
5247-537: The device—from the cathode to the anode. Adding one or more control grids within the tube enables 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 20th century and were crucial to the development of radio, television, radar, sound recording and reproduction , long-distance telephone networks, and analogue and early digital computers . While some applications had used earlier technologies such as
5346-479: The documented existence of other forms of ancient optical telegraphy . For example, one author in 1919 chose to "hazard the theory" that the Italian mainland signals from the capital of Rome that ancient Roman emperor Tiberius (42 B.C.-A.D.37, reigned A.D.14 to 37), watched for from his imperial retreat on the island of Capri . were mirror flashes, but admitted "there are no references in ancient writings to
5445-422: The electrical telegraph, the last commercial line was abandoned in 1880. On July 25, 1837, the first commercial electrical telegraph was demonstrated by English inventor Sir William Fothergill Cooke and English scientist Sir Charles Wheatstone . Both inventors viewed their device as "an improvement to the [existing] electromagnetic telegraph" and not as a new device. Samuel Morse independently developed
5544-403: The expense of increasing the channel bandwidth requirement. 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 fibres for some kinds of optical communications , coaxial cables for communications by way of
5643-544: The first programmes were transmitted on Friday, 1 May 1953, in plenty of time for the Coronation on 2 June. UHF transmissions began in 1966 with the first colour transmissions in 1970, and the VHF television signal was switched off in 1985. The Pontop Pike transmitter provides digital television transmissions to Tyne and Wear , County Durham, Tees Valley , most of Northumberland and parts of North Yorkshire . This includes
5742-647: The flash of a circular mirror is visible to the naked eye at a distance of 10 mi (16 km) for each inch of mirror diameter, and farther apart seen with a telescope . The world record distance was established by a detachment of U.S. Army signal sergeants by the inter-operation of stations in North America on Mount Ellen , ( Utah ), and Mount Uncompahgre , ( Colorado ), 183 mi (295 km) apart on 17 September 1894, with Army Signal Corps heliographs carrying mirrors only 8 in (52 cm ). The German professor Carl Friedrich Gauss (1777–1855), of
5841-482: The fort-to-fort network used for the Geronimo military campaign. It was very portable, did not require any power source, and was relatively secure since it was invisible to those not near the axis of operation, and the beam was very narrow, spreading only 50 ft (15 m) per 1 mi (1.6 km) of range. However, anyone in the beam with the correct knowledge could intercept signals without being detected. In
5940-591: The heliograph while fighting enemy Nazi German and Fascist Italian forces along the southern coast of the Mediterranean Sea in Libya and western Egypt with fellow defending British military in the desert North African campaign in 1940, 1941 and 1942. The heliograph remained standard equipment for military signallers in the Royal Australian and British armies until the 1940s, where it
6039-431: The importance of social conversations and staying connected to family and friends. 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
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#17327977399146138-607: The last-but-one transmitter group in the United Kingdom to complete digital switchover (DSO) with Northern Ireland being the last area to switch. In July 2007 it was confirmed by Ofcom that Pontop Pike would remain a C/D group after DSO. Pontop Pike underwent its 700 MHz clearance between September and November 2019 when its output moved down the band from a C/D group to a K group. Thus people with original C/D group aerials, who live in poor reception areas, may struggle to pick up some channels (see graph ). Analogue television from Pontop Pike has now ceased permanently. BBC2 analogue
6237-431: The main mirror and reflect it to the receiving station. The U.S. Army's Signal Corps heliograph used a flat square mirror that did not tilt . This type produced flashes by a shutter mounted on a second tripod (Fig 4). The heliograph had certain advantages. It allowed long-distance communication without a fixed infrastructure, though it could also be linked to make a fixed network extending for hundreds of miles, as in
6336-552: 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 brought on the first explosion of international broadcasting propaganda. 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
6435-479: The medium for transmitting signals. These networks were used for telegraphy and telephony for many decades. In the first decade of the 20th century, a revolution in wireless communication began with breakthroughs including those made in radio communications by Guglielmo Marconi , who won the 1909 Nobel Prize in Physics . Other early pioneers in electrical and electronic telecommunications include co-inventors of
6534-567: 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
6633-414: The medium into communication channels is called " time-division multiplexing " ( TDM ), and is used in optical fibre communication. Some radio communication systems use TDM within an allocated FDM channel. Hence, these systems use a hybrid of TDM and FDM. The shaping of a signal to convey information is known as modulation . Modulation can be used to represent a digital message as an analogue waveform. This
6732-742: 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 political debates in telecommunication include the reclassification of broadband Internet service as a telecommunications service (also called net neutrality ), regulation of phone spam , and expanding affordable broadband access. According to data collected by Gartner and Ars Technica sales of main consumer's telecommunication equipment worldwide in millions of units was: In
6831-596: The mid-1960s, thermionic tubes were replaced with the transistor . Thermionic tubes still have some applications for certain high-frequency amplifiers. On 11 September 1940, George Stibitz transmitted problems for his Complex Number Calculator in New York using a teletype and received the computed results back at Dartmouth College in New Hampshire . This configuration of a centralized computer ( mainframe ) with remote dumb terminals remained popular well into
6930-495: The most powerful type of visual signalling device known. In pre-radio times heliography was often the only means of communication that could span ranges of as much as 100 mi (160 km) with a lightweight portable instrument. In the United States military , by mid-1878, a younger Colonel Nelson A. Miles had established a line of heliographs connecting far-flung military outposts of Fort Keogh and Fort Custer , in
7029-452: 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
7128-400: The neighbourhood of 94.5 MHz (megahertz) while another radio station can simultaneously broadcast radio waves at frequencies in the neighbourhood of 96.1 MHz. Each radio station would transmit radio waves over a frequency bandwidth of about 180 kHz (kilohertz), centred at frequencies such as the above, which are called the "carrier frequencies" . Each station in this example
7227-439: The northern Montana Territory , a distance of 140 mi (230 km). In 1886, United States Army now General Nelson A. Miles (1839–1925), set up a network of 27 heliograph stations in the Arizona and New Mexico territories of the old Southwest during the extended campaign and hunt for the native Apache renegade chief / guerrilla warfare leader Geronimo (1829–1909). In 1890, now little-known Major W.J. Volkmar of
7326-499: The others one. The signals could either be momentary flashes, or momentary obscurations. In 1888, the U.S. Army Signal Corps reviewed all of these devices, as well as the Finley Helio-Telegraph, and finding none completely suitable, developed its own instrument of the U.S. Army Signal Corps heliograph, a two-tripod, shutter-based machine of 13 + 7 ⁄ 8 lb (6.3 kg) total weight, and ordered 100, for
7425-515: 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 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
7524-709: 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,
7623-474: The sun's motion. By 1884, all active units of the "Mangin apparatus" (a dual-mode French Army military field optical telegraph that could use either lantern or sunlight) were equipped with clockwork heliostats. The Mangin apparatus with heliostat was still in service in 1917. Proposals to automate both the modulation of the sunbeam (by clockwork) and the detection (by electrical selenium photodetectors, or photographic means) date back to at least 1882. In 1961,
7722-458: The sunbeam was pointing at the target. The flashes were produced by a keying mechanism that tilted the mirror up a few degrees at the push of a lever at the back of the instrument. If the Sun was in front of the sender, its rays were reflected directly from this mirror to the receiving station. If the Sun was behind the sender, the sighting rod was replaced by a second mirror, to capture the sunlight from
7821-422: The target was hidden by the unsilvered spot. Keeping their head still, they then adjusted the aiming rod so its cross wires bisected the target. They then turned up the sighting vane, which covered the cross wires with a diagram of a cross, and aligned the mirror with the tangent and elevation screws, so the small shadow that was the reflection of the unsilvered spot hole was on the cross target. This indicated that
7920-609: The telegraph Charles Wheatstone and Samuel Morse , numerous inventors and developers of the telephone including Antonio Meucci , Philipp Reis , Elisha Gray and Alexander Graham Bell , inventors of radio Edwin Armstrong and Lee de Forest , as well as inventors of television like Vladimir K. Zworykin , John Logie Baird and Philo Farnsworth . Since the 1960s, the proliferation of digital technologies has meant that voice communications have gradually been supplemented by data. The physical limitations of metallic media prompted
8019-412: 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
8118-556: The then Bombay Presidency of British India . Mance was familiar with heliotropes by their use earlier for the mapping project of the Great Trigonometrical Survey of India (done 1802–1871). The Mance Heliograph was operated easily by one man, and since it weighed about 7 lb (3.2 kg), the operator could readily carry the device and its supporting tripod. The British Army tested the heliograph in India at
8217-631: The then-newly discovered phenomenon of radio waves , demonstrating, by 1901, that they could be transmitted across the Atlantic Ocean. This was the start of wireless telegraphy by radio. On 17 December 1902, a transmission from the Marconi station in Glace Bay, Nova Scotia, Canada , became the world's first radio message to cross the Atlantic from North America. In 1904, a commercial service
8316-493: The time and their latitude, longitude and altitude. The solar beacons were later moved to Sather Tower at the U.C. – Berkeley campus. By June 2012, the public could specify a "custom show" of up to 32 "on" or "off" periods of 4 seconds each, permitting the transmission of a few characters of Morse Code. The designer described the Solar Beacon as a "heliostat", not a "heliograph". The first digitally controlled heliograph
8415-553: The two Russian Revolutions of 1917 , the revolutionary Bolshevik / Communist units of their Red Army during the subsequent Russian Civil War of 1918–1922, made use of a series of heliograph stations to disseminate intelligence efficiently. This continued even a decade later about counter-revolutionary basmachi rebel movements in Central Asia's Turkestan region in 1926. During World War II (1939–1945), Union of South Africa and Royal Australian military forces used
8514-541: The use of heliography for forestry protection was introduced by the United States Forestry Service in the western States. By 1920, such use was widespread in the US and beginning in the neighboring Dominion of Canada to the north, and the heliograph was regarded as "next to the telephone, the most useful communication device that is at present available for forest-protection services". D.P. Godwin of
8613-518: The use of signaling by mirrors", and that the documented means of ancient long-range visual telecommunications was by beacon fires and beacon smoke, not mirrors. Similarly, the story that a shield was used as a heliograph at the ancient famous Battle of Marathon between the Greeks and Persians in 490 B.C. is also unfortunately a modern myth, originating in the 1800s. The ancient historian Herodotus never mentioned any flash. What Herodotus did write
8712-490: The voltages and electric currents in them, and free space for communications using visible light , infrared waves, ultraviolet light , and radio waves . 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
8811-492: The wartime purposes of aircraft and land communication, radio navigation, and radar. Development of stereo FM broadcasting of radio began in the 1930s in the United States and the 1940s in the United Kingdom, displacing AM as the dominant commercial standard in the 1970s. On March 25, 1925, John Logie Baird demonstrated the transmission of moving pictures at the London department store Selfridges . Baird's device relied upon
8910-418: The world's gross domestic product (GDP). Modern telecommunication is founded on a series of key concepts that experienced progressive development and refinement in a period of well over a century: Telecommunication technologies may primarily be divided into wired and wireless methods. Overall, a basic telecommunication system consists of three main parts that are always present in some form or another: In
9009-708: Was built in 1953, by BICC with Rowridge (also 500 feet (150 m)) and North Hessary Tor in Devon (650 feet (200 m)). Its construction was brought forward by the BBC so that people in North East England could watch the Coronation of Queen Elizabeth II live on the 405-line television system VHF then in use in the UK. Test transmissions from a low-power temporary aerial began on Monday, 20 April 1953, and
9108-593: Was considered a "low probability of intercept" type of communication. The Canadian Army was the last major military force to have the heliograph as an issue item. By the time the mirror instruments were retired, they were seldom used for signalling. However, as recently as the 1980s, heliographs were used by insurgent Afghan mujahedeen forces during the Soviet invasion of Afghanistan in 1978–1979. Signal mirrors are still included in survival kits for emergency signaling to search and rescue aircraft. Most heliographs of
9207-490: Was during the Spanish Armada , when a beacon chain relayed a signal from Plymouth to London . In 1792, Claude Chappe , a French engineer, built the first fixed visual telegraphy system (or semaphore line ) between 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
9306-407: Was established to transmit nightly news summaries to subscribing ships, which incorporated them into their onboard newspapers. World War I accelerated the development of radio for military communications . After the war, commercial radio AM broadcasting began in the 1920s and became an important mass medium for entertainment and news. World War II again accelerated the development of radio for
9405-471: Was later reconfirmed, according to Article 1.3 of the ITU Radio Regulations , which defined it as "Any transmission , emission or reception of signs, signals, writings, images and sounds or intelligence of any nature by wire , radio, optical, or other electromagnetic systems". Homing pigeons have been used throughout history by different cultures. Pigeon post had Persian roots and
9504-676: Was later used by the Romans to aid their military. Frontinus claimed Julius Caesar used pigeons as messengers in his conquest of Gaul . The Greeks also conveyed the names of the victors at the Olympic Games to various cities using homing pigeons. In the early 19th century, the Dutch government used the system in Java and Sumatra . And in 1849, Paul Julius Reuter started a pigeon service to fly stock prices between Aachen and Brussels ,
9603-486: 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 and London. In 1894, Italian inventor Guglielmo Marconi began developing a wireless communication using
9702-526: Was switched off on 12 September 2012 and the remaining three on 26 September 2012. Pontop Pike never transmitted analogue Channel 5. Instead it was transmitted from Burnhope on UHF 68. Being the main broadcasting transmitter, there are also a number of relays (or repeaters) to cover patches where this transmitter can't properly serve. The following is a list of the television relays served by Pontop Pike: Telecommunications Telecommunication , often used in its plural form or abbreviated as telecom ,
9801-566: Was that someone was accused of having arranged to "hold up a shield as a signal". Suspicion grew in the later 1900s, that the flash theory was implausible. The conclusion after testing the theory was "Nobody flashed a shield at the Battle of Marathon". In a letter dated 3 June 1778, John Norris , High Sheriff of Buckinghamshire , England, notes: "Did this day heliograph intelligence from Dr [Benjamin] Franklin in Paris to Wycombe". However, there
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