1.
Satellite
–
In the context of spaceflight, a satellite is an artificial object which has been intentionally placed into orbit. Such objects are called artificial satellites to distinguish them from natural satellites such as Earths Moon. In 1957 the Soviet Union launched the worlds first artificial satellite, since then, about 6,600 satellites from more than 40 countries have been launched. According to a 2013 estimate,3,600 remained in orbit, of those, about 1,000 were operational, the rest have lived out their useful lives and become space debris. Approximately 500 operational satellites are in orbit,50 are in medium-Earth orbit. A few large satellites have been launched in parts and assembled in orbit. Over a dozen space probes have been placed into orbit around other bodies and become artificial satellites to the Moon, Mercury, Venus, Mars, Jupiter, Saturn, a few asteroids, Satellites are used for many purposes. Common types include military and civilian Earth observation satellites, communications satellites, navigation satellites, weather satellites, Space stations and human spacecraft in orbit are also satellites. Satellite orbits vary greatly, depending on the purpose of the satellite, well-known classes include low Earth orbit, polar orbit, and geostationary orbit. A launch vehicle is a rocket that throws a satellite into orbit, usually it lifts off from a launch pad on land. Some are launched at sea from a submarine or a mobile maritime platform, Satellites are usually semi-independent computer-controlled systems. Satellite subsystems attend many tasks, such as power generation, thermal control, telemetry, attitude control, the first fictional depiction of a satellite being launched into orbit was a short story by Edward Everett Hale, The Brick Moon. The idea surfaced again in Jules Vernes The Begums Fortune, in 1903, Konstantin Tsiolkovsky published Exploring Space Using Jet Propulsion Devices, which is the first academic treatise on the use of rocketry to launch spacecraft. He calculated the speed required for a minimal orbit. In 1928, Herman Potočnik published his book, The Problem of Space Travel — The Rocket Motor. He described the use of orbiting spacecraft for observation of the ground, in a 1945 Wireless World article, the English science fiction writer Arthur C. Clarke described in detail the possible use of communications satellites for mass communications. He suggested that three geostationary satellites would provide coverage over the entire planet, the first artificial satellite was Sputnik 1, launched by the Soviet Union on October 4,1957, and initiating the Soviet Sputnik program, with Sergei Korolev as chief designer. This in turn triggered the Space Race between the Soviet Union and the United States, Sputnik 1 helped to identify the density of high atmospheric layers through measurement of its orbital change and provided data on radio-signal distribution in the ionosphere
2.
London
–
London /ˈlʌndən/ is the capital and most populous city of England and the United Kingdom. Standing on the River Thames in the south east of the island of Great Britain and it was founded by the Romans, who named it Londinium. Londons ancient core, the City of London, largely retains its 1. 12-square-mile medieval boundaries. London is a global city in the arts, commerce, education, entertainment, fashion, finance, healthcare, media, professional services, research and development, tourism. It is crowned as the worlds largest financial centre and has the fifth- or sixth-largest metropolitan area GDP in the world, London is a world cultural capital. It is the worlds most-visited city as measured by international arrivals and has the worlds largest city airport system measured by passenger traffic, London is the worlds leading investment destination, hosting more international retailers and ultra high-net-worth individuals than any other city. Londons universities form the largest concentration of education institutes in Europe. In 2012, London became the first city to have hosted the modern Summer Olympic Games three times, London has a diverse range of people and cultures, and more than 300 languages are spoken in the region. Its estimated mid-2015 municipal population was 8,673,713, the largest of any city in the European Union, Londons urban area is the second most populous in the EU, after Paris, with 9,787,426 inhabitants at the 2011 census. The citys metropolitan area is the most populous in the EU with 13,879,757 inhabitants, the city-region therefore has a similar land area and population to that of the New York metropolitan area. London was the worlds most populous city from around 1831 to 1925, Other famous landmarks include Buckingham Palace, the London Eye, Piccadilly Circus, St Pauls Cathedral, Tower Bridge, Trafalgar Square, and The Shard. The London Underground is the oldest underground railway network in the world, the etymology of London is uncertain. It is an ancient name, found in sources from the 2nd century and it is recorded c.121 as Londinium, which points to Romano-British origin, and hand-written Roman tablets recovered in the city originating from AD 65/70-80 include the word Londinio. The earliest attempted explanation, now disregarded, is attributed to Geoffrey of Monmouth in Historia Regum Britanniae and this had it that the name originated from a supposed King Lud, who had allegedly taken over the city and named it Kaerlud. From 1898, it was accepted that the name was of Celtic origin and meant place belonging to a man called *Londinos. The ultimate difficulty lies in reconciling the Latin form Londinium with the modern Welsh Llundain, which should demand a form *lōndinion, from earlier *loundiniom. The possibility cannot be ruled out that the Welsh name was borrowed back in from English at a later date, and thus cannot be used as a basis from which to reconstruct the original name. Until 1889, the name London officially applied only to the City of London, two recent discoveries indicate probable very early settlements near the Thames in the London area
3.
Intelsat
–
Intelsat, S. A. is a communications satellite services provider. As of March 2017, Intelsat is to merge with Softbank backed OneWeb, the agreement is to merge in a share-for-share deal. SoftBank will buy voting and non-voting shares in the company for $1.7 billion in cash. Shares that Softbank-OneWeb will buy in the company will be bought for $5 per share. As of March 2011, Intelsat operates a fleet of 52 communications satellites and they claim to serve around 1,500 customers and employ a staff of approximately 1,100 people. The intergovernmental organization began on 20 August 1964, with 11 participating countries, on 6 April 1965, Intelsat’s first satellite, the Intelsat I, was placed in geostationary orbit above the Atlantic Ocean by a Delta D rocket. In 1973, the name was changed and there were 80 signatories, Intelsat provides service to over 600 Earth stations in more than 149 countries, territories and dependencies. By 2001, INTELSAT had over 100 members and it was also this year that INTELSAT privatized and changed its name to Intelsat. Since its inception, Intelsat has used versions of its dedicated Intelsat satellites. Intelsat completes each block of spacecraft independently, leading to a variety of contractors over the years, Intelsat’s largest spacecraft supplier is Space Systems/Loral, having built 31 spacecraft, or nearly half of the fleet. The network in its early years was not as robust as it is now. Fortunately, during the Apollo 11 moonwalk, the moon was over the Pacific Ocean, and so other antennas were used, as well as INTELSAT III, to avert the US governments interference with Intelsat, Intelsats senior management unsuccessfully considered relocating the IGO to another country. On 18 July 2001, Intelsat became a company,37 years after formation. Prior to Intelsats privatization in 2001, ownership and investment in INTELSAT was distributed among INTELSAT members according to their use of services, investment shares determined each member’s percentage of the total contribution needed to finance capital expenditures. Satellite services were available to any organization, and all paid the same rates. Today, the number of Intelsat satellites, as well as ocean-spanning fibre-optic lines, modern satellites are more robust, lasting longer with much larger capacity. Intelsat Americas-7 experienced a power failure on 29 November 2004. The satellite returned to service with reduced capacity, Intelsat was sold for U. S. $3. 1bn in January 2005 to four private equity firms, Madison Dearborn Partners, Apax Partners, Permira and Apollo Global Management
4.
Montreal
–
Montreal, officially Montréal, is the most populous municipality in the Canadian province of Quebec and the 2nd-most populous in Canada as a whole. Originally called Ville-Marie, or City of Mary, it is believed to be named after Mount Royal, the city has a distinct four-season continental climate, with warm-to-hot summers and cold, snowy winters. In 2016, Montreal had a population of 1,704,694, Montreals metropolitan area had a population of 4,098,927 and a population of 1,958,257 in the urban agglomeration, with all of the municipalities on the Island of Montreal included. Legally a French-speaking city,60. 5% of Montrealers speak French at home,21. 2% speak English and 19. 8% speak neither, Montreal is one of the most bilingual cities in Quebec and Canada, with 56% of the population able to speak both official languages. Montreal is the second-largest primarily French-speaking city in the world after Paris, historically the commercial capital of Canada, it was surpassed in population and economic strength by Toronto in the 1970s. It remains an important centre of commerce, aerospace, finance, pharmaceuticals, technology, design, education, culture, tourism, gaming, film, Montreal was also named a UNESCO City of Design. In 2009, Montreal was named North Americas leading host city for international events, according to the 2009 preliminary rankings of the International Congress. According to the 2015 Global Liveability Ranking by the Economist Intelligence Unit, in the 2017 edition of their Best Student Cities ranking, Quacquarelli Symonds ranked Montreal as the worlds best city to study abroad. Also, Montreal has 11 universities with 170,000 students enrolled, the Greater Montréal region has the highest number of university students per capita among all metropolitan areas in North America. It is the only Canadian city to have held the Summer Olympics, currently, the city hosts the Canadian Grand Prix of Formula One, the Montreal International Jazz Festival and the Just for Laughs festival. In 2012, Montreal was ranked as a Beta+ world city, in Kanien’kéha, or Mohawk language, the island is called Tiohtià, ke Tsi or Ka-wé-no-te. In Anishinaabemowin, or Ojibwe language, the land is called Mooniyaang, though the city was first named by French colonizers Ville Marie, or City of Mary, its current name comes from Mount Royal, the triple-peaked hill in the heart of the city. The most popular theory is that the name derives from Mont Réal, Cartiers 1535 diary entry, naming the mountain, according to the Commission de toponymie du Québec and the Geographical Names Board of Canada, Canadian place names have only one official form. Thus, Montreal is officially spelled with an accent over the e in both English and French. In practice, this is limited to governmental uses. English-speaking Montrealers, including English-language media, regularly omit the accent when writing in English, archaeological evidence demonstrates that First Nations native people occupied the island of Montreal as early as 4,000 years ago. By the year AD1000, they had started to cultivate maize, within a few hundred years, they had built fortified villages. Archeologists have found evidence of their habitation there and at locations in the valley since at least the 14th century
5.
Canada
–
Canada is a country in the northern half of North America. Canadas border with the United States is the worlds longest binational land border, the majority of the country has a cold or severely cold winter climate, but southerly areas are warm in summer. Canada is sparsely populated, the majority of its territory being dominated by forest and tundra. It is highly urbanized with 82 per cent of the 35.15 million people concentrated in large and medium-sized cities, One third of the population lives in the three largest cities, Toronto, Montreal and Vancouver. Its capital is Ottawa, and other urban areas include Calgary, Edmonton, Quebec City, Winnipeg. Various aboriginal peoples had inhabited what is now Canada for thousands of years prior to European colonization. Pursuant to the British North America Act, on July 1,1867, the colonies of Canada, New Brunswick and this began an accretion of provinces and territories to the mostly self-governing Dominion to the present ten provinces and three territories forming modern Canada. With the Constitution Act 1982, Canada took over authority, removing the last remaining ties of legal dependence on the Parliament of the United Kingdom. Canada is a parliamentary democracy and a constitutional monarchy, with Queen Elizabeth II being the head of state. The country is officially bilingual at the federal level and it is one of the worlds most ethnically diverse and multicultural nations, the product of large-scale immigration from many other countries. Its advanced economy is the eleventh largest in the world, relying chiefly upon its abundant natural resources, Canadas long and complex relationship with the United States has had a significant impact on its economy and culture. Canada is a country and has the tenth highest nominal per capita income globally as well as the ninth highest ranking in the Human Development Index. It ranks among the highest in international measurements of government transparency, civil liberties, quality of life, economic freedom, Canada is an influential nation in the world, primarily due to its inclusive values, years of prosperity and stability, stable economy, and efficient military. While a variety of theories have been postulated for the origins of Canada. In 1535, indigenous inhabitants of the present-day Quebec City region used the word to direct French explorer Jacques Cartier to the village of Stadacona, from the 16th to the early 18th century Canada referred to the part of New France that lay along the St. Lawrence River. In 1791, the area became two British colonies called Upper Canada and Lower Canada collectively named The Canadas, until their union as the British Province of Canada in 1841. Upon Confederation in 1867, Canada was adopted as the name for the new country at the London Conference. The transition away from the use of Dominion was formally reflected in 1982 with the passage of the Canada Act, later that year, the name of national holiday was changed from Dominion Day to Canada Day
6.
United Nations General Assembly
–
The United Nations General Assembly is one of the six principal organs of the United Nations and the only one in which all member nations have equal representation. The General Assembly is the deliberative, policymaking and representative organ of the UN. It has also established a number of subsidiary organs. It can also reconvene for special and emergency special sessions and its composition, functions, powers, voting, and procedures are set out in Chapter IV of the United Nations Charter. The first session was convened on 10 January 1946 in the Methodist Central Hall in London, other questions are decided by a straightforward majority. Each member country has one vote, apart from approval of budgetary matters, including adoption of a scale of assessment, Assembly resolutions are not binding on the members. The Assembly may make recommendations on any matters within the scope of the UN, except matters of peace, the one state, one vote power structure potentially allows states comprising just five percent of the world population to pass a resolution by a two-thirds vote. During the 1980s, the Assembly became a forum for the North-South dialogue and these issues came to the fore because of the phenomenal growth and changing makeup of the UN membership. In 1945, the UN had 51 members and it now has 193, of which more than two-thirds are developing countries. Because of their numbers, developing countries are able to determine the agenda of the Assembly, the character of its debates. For many developing countries, the UN is the source of much of their diplomatic influence, the Assembly can consider the matter immediately with a view to making recommendations to Members for collective measures to maintain or restore international peace and security. The first session of the UN General Assembly was convened on 10 January 1946 in the Methodist Central Hall in London, the next few annual sessions were held in different cities, the second session in New York, and the third session was in Paris. It moved to the permanent United Nations Headquarters in New York at the start of its seventh regular annual session, on 14 October 1952. In December 1988, in order to hear Yasser Arafat, the General Assembly organised its 29th session in the Palace of Nations, all 193 members states of the United Nations are members of the General Assembly. The agenda for each session is planned up to seven months in advance and this is refined into a provisional agenda 60 days before the opening of the session. Items on the agenda are numbered, the General Assembly votes on many resolutions brought forth by sponsoring states. These are generally statements symbolizing the sense of the community about an array of world issues. Most General Assembly resolutions are not enforceable as a legal or practical matter, the General Assembly has authority to make final decisions in some areas such as the United Nations budget
7.
Telecommunication
–
Telecommunication is the transmission of signs, signals, messages, writings, images and sounds or intelligence of any nature by wire, radio, optical or other electromagnetic systems. Telecommunication occurs when the exchange of information between communication participants includes the use of technology and it is transmitted either electrically over physical media, such as cables, or via electromagnetic radiation. Such transmission paths are divided into communication channels which afford the advantages of multiplexing. The term is used in its plural form, telecommunications. Early means of communicating over a distance included visual signals, such as beacons, smoke signals, semaphore telegraphs, signal flags, other examples of pre-modern long-distance communication included audio messages such as coded drumbeats, lung-blown horns, and loud whistles. Zworykin, John Logie Baird and Philo Farnsworth, the word telecommunication is a compound of the Greek prefix tele, meaning distant, far off, or afar, and the Latin communicare, meaning to share. Its modern use is adapted from the French, because its use was recorded in 1904 by the French engineer. Communication was first used as an English word in the late 14th century, 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 pass a single bit of information. One notable instance of their use was during the Spanish Armada, in 1792, Claude Chappe, a French engineer, built the first fixed visual telegraphy system between Lille and Paris. However semaphore suffered from the need for skilled operators and expensive towers at intervals of ten to thirty kilometres, as a result of competition from the electrical telegraph, the last commercial line was abandoned in 1880. Homing pigeons have occasionally used throughout history by different cultures. Pigeon post is thought to have Persians roots and was used by the Romans to aid their military, frontinus said that 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 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. Sir Charles Wheatstone and Sir William Fothergill Cooke invented the telegraph in 1837. Also, the first commercial electrical telegraph is purported to have constructed by Wheatstone and Cooke. Both inventors viewed their device as an improvement to the electromagnetic telegraph not as a new device, samuel Morse independently developed a version of the electrical telegraph that he unsuccessfully demonstrated on 2 September 1837
8.
History of broadcasting
–
The first broadcasting of a radio transmission consisted of Morse code was made from a temporary station set up by Guglielmo Marconi in 1895. This followed on from pioneering work in the field by Alessandro Volta, André-Marie Ampère, Georg Ohm, James Clerk Maxwell, the broadcasting of music and talk via radio started experimentally around 1905-1906, and commercially around 1920 to 1923. VHF stations started 30 to 35 years later, when people started broadcasting television the first movie that was shown was Batman curse of the green pearl it was 10 minutes long. In Britain this system was known as Electrophone, and was available as early as 1895 or 1899, in Hungary, it was called Telefon Hírmondó, and in France, Théâtrophone ). The Wikipedia Telefon Hírmondó page includes a 1907 program guide which looks similar to the types of schedules used by many broadcasting stations some 20 or 30 years later. By the 1950s, virtually every country had a broadcasting system, today, most countries have evolved into a dual system, including the UK. By 1955, practically every family in North America and Western Europe, a dramatic change came in the 1960s with the introduction of small inexpensive portable transistor radio, the greatly expanded ownership and usage. Access became practically universal across the world, Australia developed its own system, through its own engineers, manufacturers, retailers, newspapers, entertainment services, and news agencies. The government set up the first radio system, and business interests marginalized the hobbyists, the Labor Party was especially interested in radio because it allowed them to bypass the newspapers, which were mostly controlled by the opposition. Both parties agreed on the need for a system, and in 1932 set up the Australian Broadcasting Commission. The first commercial broadcasters, originally known as B class stations, were on the air as early as 1925, the number of stations remained relatively dormant throughout World War II and in the post-war era. The broadcasting system was deregulated in 1992, except that there were limits on foreign ownership. By 2000,99 percent of Australians owned at least one television set, Australian radio hams can be traced to the early 1900s. The 1905 Wireless Telegraphy Act whilst acknowledging the existence of wireless telgraphy, in 1906, the first official Morse code transmission in Australia was by the Marconi Company between Queenscliff, Victoria and Devonport, Tasmania. The first broadcast of music was made during a demonstration on 13 August 1919 by Ernest Fisk of AWA – Amalgamated Wireless, a number of amateurs commenced broadcasting music in 1920 and 1921. 2CM was run by Charles MacLuran who started the station in 1921 with regular Sunday evening broadcasts from the Wentworth Hotel, 2CM is often regarded as Australias first, regular, non-official station. It was not until November 1923 when the government finally gave its approval for a number of officially recognised medium wave stations, all stations operated under a unique Sealed Set system under which each set was sealed to the frequency of one station. Part of the price of the set went to the government via the Postmaster-Generals Department, apart from extremely limited advertising, this was the broadcasters only source of income
9.
Electrical telegraph
–
An electrical telegraph is a telegraph that uses electrical signals, usually conveyed via dedicated telecommunication lines or radio. From early studies of electricity, electrical phenomena were known to travel with great speed, in 1753 an anonymous writer in the Scots Magazine suggested an electrostatic telegraph. In 1774 Georges-Louis Le Sage realised an early electric telegraph, the telegraph had a separate wire for each of the 26 letters of the alphabet and its range was only between two rooms of his home. In 1800 Alessandro Volta invented the voltaic pile, allowing for a current of electricity for experimentation. Both their designs employed multiple wires to represent almost all Latin letters, thus, messages could be conveyed electrically up to a few kilometers, with each of the telegraph receivers wires immersed in a separate glass tube of acid. The telegraph receivers operator would watch the bubbles and could record the transmitted message. This is in contrast to later telegraphs that used a single wire, hans Christian Ørsted discovered in 1820 that an electric current produces a magnetic field which will deflect a compass needle. In the same year Johann Schweigger invented the galvanometer, with a coil of wire around a compass, in 1824, Peter Barlow said that such a system only worked to a distance of about 200 feet, and so was impractical. In 1825 William Sturgeon invented the electromagnet, with a winding of uninsulated wire on a piece of varnished iron. During his tenure at The Albany Academy from 1826 to 1832, in 1835 Joseph Henry and Edward Davy invented the critical electrical relay. Davys relay used a needle which dipped into a mercury contact when an electric current passed through the surrounding coil. This allowed a weak current to switch a larger current to operate a powerful local electromagnet over very long distances, Davy demonstrated his telegraph system in Regents Park in 1837 and was granted a patent on 4 July 1838. He also developed an electric relay, the first working telegraph was built by the English inventor Francis Ronalds in 1816 and used static electricity. At the family home on Hammersmith Mall, he set up a subterranean system in a 175 yard long trench as well as an eight mile long overhead telegraph. The lines were connected at both ends to revolving dials marked with the letters of the alphabet and electrical impulses sent along the wire were used to transmit messages, offering his invention to the Admiralty in July 1816, it was rejected as “wholly unnecessary”. Elements of Ronalds’ design were utilised in the subsequent commercialisation of the telegraph over 20 years later, the telegraph invented by Baron Schilling von Canstatt in 1832 had a transmitting device which consisted of a keyboard with 16 black-and-white keys. These served for switching the electric current, the receiving instrument consisted of six galvanometers with magnetic needles, suspended from silk threads. Both stations of Shillings telegraph were connected by eight wires, six were connected with the galvanometers, one served for the return current, when at the starting station the operator pressed a key, the corresponding pointer was deflected at the receiving station
10.
Fax
–
Fax, sometimes called telecopying or telefax, is the telephonic transmission of scanned printed material, normally to a telephone number connected to a printer or other output device. The receiving fax machine interprets the tones and reconstructs the image, early systems used direct conversions of image darkness to audio tone in a continuous or analog manner. Since the 1980s, most machines modulate the audio frequencies using a digital representation of the page which is compressed to quickly transmit areas which are all-white or all-black. Scottish inventor Alexander Bain worked on chemical mechanical fax type devices and he received British patent 9745 on May 27,1843 for his Electric Printing Telegraph. Frederick Bakewell made several improvements on Bains design and demonstrated a telefax machine, the Pantelegraph was invented by the Italian physicist Giovanni Caselli. He introduced the first commercial service between Paris and Lyon in 1865, some 11 years before the invention of the telephone. In 1880, English inventor Shelford Bidwell constructed the scanning phototelegraph that was the first telefax machine to scan any two-dimensional original, previously, photographs had been sent over the radio using this process. The Western Union Deskfax fax machine, announced in 1948, was a machine that fit comfortably on a desktop. As a designer for the Radio Corporation of America, in 1924, Richard H. Ranger invented the wireless photoradiogram, or transoceanic radio facsimile, the forerunner of today’s fax machines. A photograph of President Calvin Coolidge sent from New York to London on November 29,1924 became the first photo picture reproduced by transoceanic radio facsimile, commercial use of Ranger’s product began two years later. Also in 1924, Herbert E. Ives of AT&T Corporation transmitted and reconstructed the first color facsimile, around 1952 or so, Finch Facsimile, a highly developed machine, was described in detail in a book, it was never manufactured in quantity. By the late 1940s, radiofax receivers were sufficiently miniaturized to be fitted beneath the dashboard of Western Unions Telecar telegram delivery vehicles, in the 1960s, the United States Army transmitted the first photograph via satellite facsimile to Puerto Rico from the Deal Test Site using the Courier satellite. Radio fax is still in limited use today for transmitting weather charts, in 1964, Xerox Corporation introduced what many consider to be the first commercialized version of the modern fax machine, under the name or Long Distance Xerography. This model was superseded two years later with a unit that would set the standard for fax machines for years to come. Up until this point facsimile machines were expensive and hard to operate. In 1966, Xerox released the Magnafax Telecopiers, a smaller and this unit was far easier to operate and could be connected to any standard telephone line. This machine was capable of transmitting a letter-sized document in about six minutes, the first sub-minute, digital fax machine was developed by Dacom, which built on digital data compression technology originally developed at Lockheed for satellite communication. By the late 1970s, many companies around the world, entered the fax market, very shortly after a new wave of more compact, faster and efficient fax machines would hit the market
11.
Heliograph
–
A heliograph is a wireless solar telegraph that signals by flashes of sunlight 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 century. Its main uses were military, survey and forest protection work, heliographs were standard issue in the British and Australian armies until the 1960s, and were used by the Pakistani army as late as 1975. Most heliographs were variants of the British Army Mance Mark V version and it used a mirror with a small unsilvered spot in the centre. The sender aligned the heliograph to the target by looking at the target in the mirror. Keeping his head still, he adjusted the aiming rod so its cross wires bisected the target. This indicated that 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 rod was replaced by a second mirror, to capture the sunlight from the main mirror. The U. S. Signal Corps heliograph mirror did not tilt and this type produced flashes by a shutter mounted on a second tripod. The heliograph had some great advantages, however, anyone in the beam with the correct knowledge could intercept signals without being detected. In the Boer War, where both sides used heliographs, tubes were used to decrease the dispersion of the beam.5 degrees to 15 degrees. The distance that signals could be seen depended on the clarity of the sky. A clear line of sight was required, and since the Earths surface is curved, under ordinary conditions, a flash could be seen 30 miles with the naked eye, and much farther with a telescope. The maximum range was considered to be 10 miles for each inch of mirror diameter, mirrors ranged from 1.5 inches to 12 inches or more. The record distance was established by a detachment of U. S, the German professor Carl Friedrich Gauss of the University of Göttingen developed and used a predecessor of the heliograph in 1821. His device directed a beam of sunlight to a distant station to be used as a marker for geodetic survey work. Similarly, the story that a shield was used as a heliograph at the Battle of Marathon is a modern myth, what Herodotus did write was that someone was accused of having arranged to hold up a shield as a signal
12.
History of the Internet
–
The history of the Internet begins with the development of electronic computers in the 1950s. Initial concepts of packet networking originated in several science laboratories in the United States, United Kingdom. The US Department of Defense awarded contracts as early as the 1960s for packet network systems, including the development of the ARPANET. Packet switching networks such as ARPANET, NPL network, CYCLADES, Merit Network, Tymnet, Donald Davies first designed a packet-switched network at the National Physics Laboratory in the UK, which became a testbed for UK research for almost two decades. The ARPANET project led to the development of protocols for internetworking, Access to the ARPANET was expanded in 1981 when the National Science Foundation funded the Computer Science Network. In 1982, the Internet protocol suite was introduced as the networking protocol on the ARPANET. Commercial Internet service providers began to emerge in the very late 1980s, the ARPANET was decommissioned in 1990. The research and education community continues to develop and use advanced networks such as NSFs very high speed Backbone Network Service, Internet2, increasing amounts of data are transmitted at higher and higher speeds over fiber optic networks operating at 1-Gbit/s, 10-Gbit/s, or more. Today the Internet continues to grow, driven by ever greater amounts of information, commerce, entertainment. Such communication systems were limited to point to point communication between two end devices. Telegraph systems and telex machines can be considered precursors of this kind of communication. The Telegraph in the late 19th century was the first fully digital communication system, fundamental theoretical work in data transmission and information theory was developed by Claude Shannon, Harry Nyquist, and Ralph Hartley in the early 20th century. Early computers had a processing unit and remote terminals. As the technology evolved, new systems were devised to allow communication over longer distances or with higher speed that were necessary for the computer model. These technologies made it possible to exchange data between remote computers, however, the point-to-point communication model was limited, as it did not allow for direct communication between any two arbitrary systems, a physical link was necessary. The technology was considered unsafe for strategic and military use because there were no alternative paths for the communication in case of an enemy attack. With limited exceptions, the earliest computers were connected directly to terminals used by individual users, such networks became known as local-area networks. Networking beyond this scope, known as wide-area networks, emerged during the 1950s, J. C. R. Licklider, Vice President at Bolt Beranek and Newman, Inc
