World War I
World War I known as the First World War or the Great War, was a global war originating in Europe that lasted from 28 July 1914 to 11 November 1918. Contemporaneously described as "the war to end all wars", it led to the mobilisation of more than 70 million military personnel, including 60 million Europeans, making it one of the largest wars in history, it is one of the deadliest conflicts in history, with an estimated nine million combatants and seven million civilian deaths as a direct result of the war, while resulting genocides and the 1918 influenza pandemic caused another 50 to 100 million deaths worldwide. On 28 June 1914, Gavrilo Princip, a Bosnian Serb Yugoslav nationalist, assassinated the Austro-Hungarian heir Archduke Franz Ferdinand in Sarajevo, leading to the July Crisis. In response, on 23 July Austria-Hungary issued an ultimatum to Serbia. Serbia's reply failed to satisfy the Austrians, the two moved to a war footing. A network of interlocking alliances enlarged the crisis from a bilateral issue in the Balkans to one involving most of Europe.
By July 1914, the great powers of Europe were divided into two coalitions: the Triple Entente—consisting of France and Britain—and the Triple Alliance of Germany, Austria-Hungary and Italy. Russia felt it necessary to back Serbia and, after Austria-Hungary shelled the Serbian capital of Belgrade on the 28th, partial mobilisation was approved. General Russian mobilisation was announced on the evening of 30 July; when Russia failed to comply, Germany declared war on 1 August in support of Austria-Hungary, with Austria-Hungary following suit on 6th. German strategy for a war on two fronts against France and Russia was to concentrate the bulk of its army in the West to defeat France within four weeks shift forces to the East before Russia could mobilise. On 2 August, Germany demanded free passage through Belgium, an essential element in achieving a quick victory over France; when this was refused, German forces invaded Belgium on 3 August and declared war on France the same day. On 12 August and France declared war on Austria-Hungary.
In November 1914, the Ottoman Empire entered the war on the side of the Alliance, opening fronts in the Caucasus and the Sinai Peninsula. The war was fought in and drew upon each power's colonial empire as well, spreading the conflict to Africa and across the globe; the Entente and its allies would become known as the Allied Powers, while the grouping of Austria-Hungary and their allies would become known as the Central Powers. The German advance into France was halted at the Battle of the Marne and by the end of 1914, the Western Front settled into a battle of attrition, marked by a long series of trench lines that changed little until 1917. In 1915, Italy opened a front in the Alps. Bulgaria joined the Central Powers in 1915 and Greece joined the Allies in 1917, expanding the war in the Balkans; the United States remained neutral, although by doing nothing to prevent the Allies from procuring American supplies whilst the Allied blockade prevented the Germans from doing the same the U. S. became an important supplier of war material to the Allies.
After the sinking of American merchant ships by German submarines, the revelation that the Germans were trying to incite Mexico to make war on the United States, the U. S. declared war on Germany on 6 April 1917. Trained American forces would not begin arriving at the front in large numbers until mid-1918, but the American Expeditionary Force would reach some two million troops. Though Serbia was defeated in 1915, Romania joined the Allied Powers in 1916 only to be defeated in 1917, none of the great powers were knocked out of the war until 1918; the 1917 February Revolution in Russia replaced the Tsarist autocracy with the Provisional Government, but continuing discontent at the cost of the war led to the October Revolution, the creation of the Soviet Socialist Republic, the signing of the Treaty of Brest-Litovsk by the new government in March 1918, ending Russia's involvement in the war. This allowed the transfer of large numbers of German troops from the East to the Western Front, resulting in the German March 1918 Offensive.
This offensive was successful, but the Allies rallied and drove the Germans back in their Hundred Days Offensive. Bulgaria was the first Central Power to sign an armistice—the Armistice of Salonica on 29 September 1918. On 30 October, the Ottoman Empire capitulated. On 4 November, the Austro-Hungarian empire agreed to the Armistice of Villa Giusti after being decisively defeated by Italy in the Battle of Vittorio Veneto. With its allies defeated, revolution at home, the military no longer willing to fight, Kaiser Wilhelm abdicated on 9 November and Germany signed an armistice on 11 November 1918. World War I was a significant turning point in the political, cultural and social climate of the world; the war and its immediate aftermath sparked numerous uprisings. The Big Four (Britain, the United States, It
Television, sometimes shortened to tele or telly, is a telecommunication medium used for transmitting moving images in monochrome, or in color, in two or three dimensions and sound. The term can refer to a television set, a television program, or the medium of television transmission. Television is a mass medium for advertising and news. Television became available in crude experimental forms in the late 1920s, but it would still be several years before the new technology would be marketed to consumers. After World War II, an improved form of black-and-white TV broadcasting became popular in the United States and Britain, television sets became commonplace in homes and institutions. During the 1950s, television was the primary medium for influencing public opinion. In the mid-1960s, color broadcasting was introduced in most other developed countries; the availability of multiple types of archival storage media such as Betamax, VHS tape, local disks, DVDs, flash drives, high-definition Blu-ray Discs, cloud digital video recorders has enabled viewers to watch pre-recorded material—such as movies—at home on their own time schedule.
For many reasons the convenience of remote retrieval, the storage of television and video programming now occurs on the cloud. At the end of the first decade of the 2000s, digital television transmissions increased in popularity. Another development was the move from standard-definition television to high-definition television, which provides a resolution, higher. HDTV may be transmitted in various formats: 1080p, 720p. Since 2010, with the invention of smart television, Internet television has increased the availability of television programs and movies via the Internet through streaming video services such as Netflix, Amazon Video, iPlayer and Hulu. In 2013, 79 % of the world's households owned; the replacement of early bulky, high-voltage cathode ray tube screen displays with compact, energy-efficient, flat-panel alternative technologies such as LCDs, OLED displays, plasma displays was a hardware revolution that began with computer monitors in the late 1990s. Most TV sets sold in the 2000s were flat-panel LEDs.
Major manufacturers announced the discontinuation of CRT, DLP, fluorescent-backlit LCDs by the mid-2010s. In the near future, LEDs are expected to be replaced by OLEDs. Major manufacturers have announced that they will produce smart TVs in the mid-2010s. Smart TVs with integrated Internet and Web 2.0 functions became the dominant form of television by the late 2010s. Television signals were distributed only as terrestrial television using high-powered radio-frequency transmitters to broadcast the signal to individual television receivers. Alternatively television signals are distributed by coaxial cable or optical fiber, satellite systems and, since the 2000s via the Internet; until the early 2000s, these were transmitted as analog signals, but a transition to digital television is expected to be completed worldwide by the late 2010s. A standard television set is composed of multiple internal electronic circuits, including a tuner for receiving and decoding broadcast signals. A visual display device which lacks a tuner is called a video monitor rather than a television.
The word television comes from Ancient Greek τῆλε, meaning'far', Latin visio, meaning'sight'. The first documented usage of the term dates back to 1900, when the Russian scientist Constantin Perskyi used it in a paper that he presented in French at the 1st International Congress of Electricity, which ran from 18 to 25 August 1900 during the International World Fair in Paris; the Anglicised version of the term is first attested in 1907, when it was still "...a theoretical system to transmit moving images over telegraph or telephone wires". It was "...formed in English or borrowed from French télévision." In the 19th century and early 20th century, other "...proposals for the name of a then-hypothetical technology for sending pictures over distance were telephote and televista." The abbreviation "TV" is from 1948. The use of the term to mean "a television set" dates from 1941; the use of the term to mean "television as a medium" dates from 1927. The slang term "telly" is more common in the UK; the slang term "the tube" or the "boob tube" derives from the bulky cathode ray tube used on most TVs until the advent of flat-screen TVs.
Another slang term for the TV is "idiot box". In the 1940s and throughout the 1950s, during the early rapid growth of television programming and television-set ownership in the United States, another slang term became used in that period and continues to be used today to distinguish productions created for broadcast on television from films developed for presentation in movie theaters; the "small screen", as both a compound adjective and noun, became specific references to television, while the "big screen" was used to identify productions made for theatrical release. Facsimile transmission systems for still photographs pioneered methods of mechanical scanning of images in the early 19th century. Alexander Bain introduced the facsimile machine between 1843 and 1846. Frederick Bakewell demonstrated a working laboratory version in 1851. Willoughby Smith discovered the photoconductivity of the element selenium in 1873; as a 23-year-old German university student, Paul Julius Gottlieb Nipkow proposed and patented the Nipkow disk in 1884.
This was a spinning disk with a spiral pattern of holes in it, so each hole scanned a line of the image. Although he never built a working model
In computer architecture, a bus is a communication system that transfers data between components inside a computer, or between computers. This expression covers all related hardware components and software, including communication protocols. Early computer buses were parallel electrical wires with multiple hardware connections, but the term is now used for any physical arrangement that provides the same logical function as a parallel electrical bus. Modern computer buses can use both parallel and bit serial connections, can be wired in either a multidrop or daisy chain topology, or connected by switched hubs, as in the case of USB. Computer systems consist of three main parts: the central processing unit that processes data, memory that holds the programs and data to be processed, I/O devices as peripherals that communicate with the outside world. An early computer might contain a hand-wired CPU of vacuum tubes, a magnetic drum for main memory, a punch tape and printer for reading and writing data respectively.
A modern system might have a multi-core CPU, DDR4 SDRAM for memory, a solid-state drive for secondary storage, a graphics card and LCD as a display system, a mouse and keyboard for interaction, a Wi-Fi connection for networking. In both examples, computer buses of one form or another move data between all of these devices. In most traditional computer architectures, the CPU and main memory tend to be coupled. A microprocessor conventionally is a single chip which has a number of electrical connections on its pins that can be used to select an "address" in the main memory and another set of pins to read and write the data stored at that location. In most cases, the CPU and memory share signalling operate in synchrony; the bus connecting the CPU and memory is one of the defining characteristics of the system, referred to as the system bus. It is possible to allow peripherals to communicate with memory in the same fashion, attaching adaptors in the form of expansion cards directly to the system bus.
This is accomplished through some sort of standardized electrical connector, several of these forming the expansion bus or local bus. However, as the performance differences between the CPU and peripherals varies some solution is needed to ensure that peripherals do not slow overall system performance. Many CPUs feature a second set of pins similar to those for communicating with memory, but able to operate at different speeds and using different protocols. Others use smart controllers to place the data directly in memory, a concept known as direct memory access. Most modern systems combine both solutions; as the number of potential peripherals grew, using an expansion card for every peripheral became untenable. This has led to the introduction of bus systems designed to support multiple peripherals. Common examples are the SATA ports in modern computers, which allow a number of hard drives to be connected without the need for a card. However, these high-performance systems are too expensive to implement in low-end devices, like a mouse.
This has led to the parallel development of a number of low-performance bus systems for these solutions, the most common example being the standardized Universal Serial Bus. All such examples may be referred to as peripheral buses, although this terminology is not universal. In modern systems the performance difference between the CPU and main memory has grown so great that increasing amounts of high-speed memory is built directly into the CPU, known as a cache. In such systems, CPUs communicate using high-performance buses that operate at speeds much greater than memory, communicate with memory using protocols similar to those used for peripherals in the past; these system buses are used to communicate with most other peripherals, through adaptors, which in turn talk to other peripherals and controllers. Such systems are architecturally more similar to multicomputers, communicating over a bus rather than a network. In these cases, expansion buses are separate and no longer share any architecture with their host CPU.
What would have been a system bus is now known as a front-side bus. Given these changes, the classical terms "system", "expansion" and "peripheral" no longer have the same connotations. Other common categorization systems are based on the bus's primary role, connecting devices internally or externally, PCI vs. SCSI for instance. However, many common modern bus systems can be used for both. Other examples, like InfiniBand and I²C were designed from the start to be used both internally and externally; the internal bus known as internal data bus, memory bus, system bus or Front-Side-Bus, connects all the internal components of a computer, such as CPU and memory, to the motherboard. Internal data buses are referred to as a local bus, because they are intended to connect to local devices; this bus is rather quick and is independent of the rest of the computer operations. The external bus, or expansion bus, is made up of the electronic pathways that connect the different external devices, such as printer etc. to the computer.
Buses can be parallel buses, which carry data words in parallel on multiple wires, or serial buses, which carry data in bit-serial form. The addition of extra power and control connections, differential
A communications satellite is an artificial satellite that relays and amplifies radio telecommunications signals via a transponder. Communications satellites are used for television, radio and military applications. There are 2,134 communications satellites in Earth’s orbit, used by both private and government organizations. Many are in geostationary orbit 22,200 miles above the equator, so that the satellite appears stationary at the same point in the sky, so the satellite dish antennas of ground stations can be aimed permanently at that spot and do not have to move to track it; the high frequency radio waves used for telecommunications links travel by line of sight and so are obstructed by the curve of the Earth. The purpose of communications satellites is to relay the signal around the curve of the Earth allowing communication between separated geographical points. Communications satellites use a wide range of microwave frequencies. To avoid signal interference, international organizations have regulations for which frequency ranges or "bands" certain organizations are allowed to use.
This allocation of bands minimizes the risk of signal interference. The concept of the geostationary communications satellite was first proposed by Arthur C. Clarke, along with Vahid K. Sanadi building on work by Konstantin Tsiolkovsky. In October 1945 Clarke published an article titled "Extraterrestrial Relays" in the British magazine Wireless World; the article described the fundamentals behind the deployment of artificial satellites in geostationary orbits for the purpose of relaying radio signals. Thus, Arthur C. Clarke is quoted as being the inventor of the communications satellite and the term'Clarke Belt' employed as a description of the orbit. Decades a project named Communication Moon Relay was a telecommunication project carried out by the United States Navy, its objective was to develop a secure and reliable method of wireless communication by using the Moon as a passive reflector and a natural communications satellite. The first artificial Earth satellite was Sputnik 1. Put into orbit by the Soviet Union on October 4, 1957, it was equipped with an on-board radio-transmitter that worked on two frequencies: 20.005 and 40.002 MHz.
Sputnik 1 was launched as a major step in the exploration of rocket development. However, it was not placed in orbit for the purpose of sending data from one point on earth to another; the first satellite to relay communications was an intended lunar probe. Though the spacecraft only made it about halfway to the moon, it flew high enough to carry out the proof of concept relay of telemetry across the world, first from Cape Canaveral to Manchester, England; the first satellite purpose-built to relay communications was NASA's Project SCORE in 1958, which used a tape recorder to store and forward voice messages. It was used to send a Christmas greeting to the world from U. S. President Dwight D. Eisenhower. Courier 1B, built by Philco, launched in 1960, was the world's first active repeater satellite; the first artificial satellite used to further advances in global communications was a balloon named Echo 1. Echo 1 was the world's first artificial communications satellite capable of relaying signals to other points on Earth.
It soared 1,600 kilometres above the planet after its Aug. 12, 1960 launch, yet relied on humanity's oldest flight technology — ballooning. Launched by NASA, Echo 1 was a 30-metre aluminized PET film balloon that served as a passive reflector for radio communications; the world's first inflatable satellite — or "satelloon", as they were informally known — helped lay the foundation of today's satellite communications. The idea behind a communications satellite is simple: Send data up into space and beam it back down to another spot on the globe. Echo 1 accomplished this by serving as an enormous mirror, 10 stories tall, that could be used to reflect communications signals. There are two major classes of communications satellites and active. Passive satellites only reflect the signal coming from the source, toward the direction of the receiver. With passive satellites, the reflected signal is not amplified at the satellite, only a small amount of the transmitted energy reaches the receiver. Since the satellite is so far above Earth, the radio signal is attenuated due to free-space path loss, so the signal received on Earth is very weak.
Active satellites, on the other hand, amplify the received signal before retransmitting it to the receiver on the ground. Passive satellites are little used now. Telstar was the second direct relay communications satellite. Belonging to AT&T as part of a multi-national agreement between AT&T, Bell Telephone Laboratories, NASA, the British General Post Office, the French National PTT to develop satellite communications, it was launched by NASA from Cape Canaveral on July 10, 1962, in the first sponsored space launch. Relay 1 was launched on December 13, 1962, it became the first satellite to transmit across the Pacific Ocean on November 22, 1963. An immediate antecedent of the geostationary satellites was the Hughes Aircraft Company's Syncom 2, launched on July 26, 1963. Syncom 2 was the first communications satellite in a geosynchronous orbit, it revolved around the earth once per day at constant speed, but because it still had north-south motion, special equipment was needed to track it. Its successor, Syncom 3 was the first geostationary communications satellite.
Syncom 3 obt
A semaphore telegraph is an early system of conveying information by means of visual signals, using towers with pivoting shutters known as blades or paddles. Information is encoded by the position of the mechanical elements; the most used system was invented in 1792 in France by Claude Chappe, was popular in the late eighteenth to early nineteenth centuries. Lines of relay towers with a semaphore rig at the top were built within line-of-sight of each other, at separations of 5–20 miles. Operators at each tower would watch the neighboring tower through a spyglass, when the semaphore arms began to move spelling out a message, they would pass the message on to the next tower; this system was much faster than post riders for conveying a message over long distances, had cheaper long-term operating costs, once constructed. Semaphore lines were a precursor of the electrical telegraph, which would replace them half a century and would be cheaper and more private; the line-of-sight distance between relay stations was limited by geography and weather, prevented the optical telegraph from crossing wide expanses of water, unless a convenient island could be used for a relay station.
Modern derivatives of the semaphore system include the heliograph. The word semaphore was coined in 1801 by the French inventor of the semaphore line itself, Claude Chappe, he composed it from the Greek elements σῆμα. Chappe coined the word tachygraph, meaning "fast writer". However, the French Army preferred to call Chappe's semaphore system the telegraph, meaning "far writer", coined by French statesman André François Miot de Mélito; the word semaphoric was first printed in English in 1808: "The newly constructed Semaphoric telegraphs", referring to the destruction of telegraphs in France. The word semaphore was first printed in English in 1816: "The improved Semaphore has been erected on the top of the Admiralty", referring to the installation of a simpler telegraph invented by Sir Home Popham. Semaphore telegraphs are called "optical telegraphs", "shutter telegraph chains", "Chappe telegraphs" or "Napoleonic semaphore". Optical telegraphy dates from ancient times, in the form of hydraulic telegraphs and smoke signals.
Modern design of semaphores was first foreseen by the British polymath Robert Hooke, who gave a vivid and comprehensive outline of visual telegraphy to the Royal Society in a 1684 submission in which he outlined many practical details. The system was never put into practice. One of the first experiments of optical signalling was carried out by the Anglo-Irish landowner and inventor, Sir Richard Lovell Edgeworth in 1767, he placed a bet with his friend, the horse racing gambler Lord March, that he could transmit knowledge of the outcome of the race in just one hour. Using a network of signalling sections erected on high ground, the signal would be observed from one station to the next by means of a telescope; the signal itself consisted of a large pointer that could be placed into eight possible positions in 45 degree increments. A series of two such signals gave a total 64 code elements and a third signal took it up to 512, he returned to his idea after hearing of Chappe's system. Credit for the first successful optical telegraph goes to the French engineer Claude Chappe and his brothers in 1792, who succeeded in covering France with a network of 556 stations stretching a total distance of 4,800 kilometres.
Le système Chappe was used for national communications until the 1850s. During 1790–1795, at the height of the French Revolution, France needed a swift and reliable communication system to thwart the war efforts of its enemies. France was surrounded by the forces of Britain, the Netherlands, Prussia and Spain, the cities of Marseille and Lyon were in revolt, the British Fleet held Toulon; the only advantage France held was the lack of cooperation between the allied forces due to their inadequate lines of communication. In the summer of 1790, the Chappe brothers set about devising a system of communication that would allow the central government to receive intelligence and to transmit orders in the shortest possible time. On 2 March 1791 at 11am, they sent the message “si vous réussissez, vous serez bientôt couverts de gloire” between Brulon and Parce, a distance of 16 kilometres; the first means used a combination of black and white panels, clocks and codebooks to send their message. The Chappes carried out experiments during the next two years, on two occasions their apparatus at Place de l'Étoile, Paris was destroyed by mobs who thought they were communicating with royalist forces.
However, in the summer of 1792 Claude was appointed Ingénieur-Télégraphiste and charged with establishing a line of stations between Paris and Lille, a distance of 230 kilometres. It was used to carry dispatches for the war between Austria. In 1794, it brought news of a French capture of Condé-sur-l'Escaut from the Austrians less than an hour after it occurred; the first symbol of a message to Lille would pass through 15 stations in only nine minutes. The speed of the line varied with the weather, but the line to Lille transferred 36 symbols, a complete message, in about 32 minutes. Another line of 50 stations was completed in 1798, covering 488 km betwe
Jerusalem is a city in the Middle East, located on a plateau in the Judaean Mountains between the Mediterranean and the Dead Sea. It is one of the oldest cities in the world, is considered holy to the three major Abrahamic religions—Judaism and Islam. Both Israel and the Palestinian Authority claim Jerusalem as their capital, as Israel maintains its primary governmental institutions there and the State of Palestine foresees it as its seat of power. During its long history, Jerusalem has been destroyed at least twice, besieged 23 times and recaptured 44 times, attacked 52 times; the part of Jerusalem called the City of David shows first signs of settlement in the 4th millennium BCE, in the shape of encampments of nomadic shepherds. Jerusalem was named as "Urusalim" on ancient Egyptian tablets meaning "City of Shalem" after a Canaanite deity, during the Canaanite period. During the Israelite period, significant construction activity in Jerusalem began in the 9th century BCE, in the 8th century the city developed into the religious and administrative center of the Kingdom of Judah.
In 1538, the city walls were rebuilt for a last time around Jerusalem under Suleiman the Magnificent. Today those walls define the Old City, traditionally divided into four quarters—known since the early 19th century as the Armenian, Christian and Muslim Quarters; the Old City became a World Heritage Site in 1981, is on the List of World Heritage in Danger. Since 1860 Jerusalem has grown far beyond the Old City's boundaries. In 2015, Jerusalem had a population of some 850,000 residents, comprising 200,000 secular Jewish Israelis, 350,000 Haredi Jews and 300,000 Palestinians. In 2011, the population numbered 801,000, of which Jews comprised 497,000, Muslims 281,000, Christians 14,000 and 9,000 were not classified by religion. According to the Bible, King David conquered the city from the Jebusites and established it as the capital of the united kingdom of Israel, his son, King Solomon, commissioned the building of the First Temple. Modern scholars argue that Jews branched out of the Canaanite peoples and culture through the development of a distinct monolatrous — and monotheistic — religion centered on El/Yahweh, one of the Ancient Canaanite deities.
These foundational events, straddling the dawn of the 1st millennium BCE, assumed central symbolic importance for the Jewish people. The sobriquet of holy city was attached to Jerusalem in post-exilic times; the holiness of Jerusalem in Christianity, conserved in the Septuagint which Christians adopted as their own authority, was reinforced by the New Testament account of Jesus's crucifixion there. In Sunni Islam, Jerusalem is the third-holiest city, after Medina. In Islamic tradition, in 610 CE it became the first qibla, the focal point for Muslim prayer, Muhammad made his Night Journey there ten years ascending to heaven where he speaks to God, according to the Quran; as a result, despite having an area of only 0.9 square kilometres, the Old City is home to many sites of seminal religious importance, among them the Temple Mount with its Western Wall, Dome of the Rock and al-Aqsa Mosque, the Church of the Holy Sepulchre. Outside the Old City stands the Garden Tomb. Today, the status of Jerusalem remains one of the core issues in the Israeli–Palestinian conflict.
During the 1948 Arab–Israeli War, West Jerusalem was among the areas captured and annexed by Israel while East Jerusalem, including the Old City, was captured and annexed by Jordan. Israel captured East Jerusalem from Jordan during the 1967 Six-Day War and subsequently annexed it into Jerusalem, together with additional surrounding territory. One of Israel's Basic Laws, the 1980 Jerusalem Law, refers to Jerusalem as the country's undivided capital. All branches of the Israeli government are located in Jerusalem, including the Knesset, the residences of the Prime Minister and President, the Supreme Court. While the international community rejected the annexation as illegal and treats East Jerusalem as Palestinian territory occupied by Israel, Israel has a stronger claim to sovereignty over West Jerusalem. A city called Rušalim in the execration texts of the Middle Kingdom of Egypt is but not universally, identified as Jerusalem. Jerusalem is called Urušalim in the Amarna letters of Abdi-Heba.
The name "Jerusalem" is variously etymologized to mean "foundation of the god Shalem". Shalim or Shalem was the name of the god of dusk in the Canaanite religion, whose name is based on the same root S-L-M from which the Hebrew word for "peace" is derived; the name thus offered itself to etymologizations such as "The City of Peace", "Abode of Peace", "dwelling of peace", alternately "Vision of Peace" in some Christian authors. The ending -ayim indicates the dual, thus leading to the suggestion that the name Yerushalayim refers to the fact that the city sat on two hills; the form Yerushalem or Yerushalayim first appears in the Book of Joshua. According to a Midrash, the name is a combination of "Yireh" and "Shalem" the two names were un
A beacon is an intentionally conspicuous device designed to attract attention to a specific location. A common example is the lighthouse, which provides a fixed location that can used to navigate around obsticals or into port. More modern examples include a variety of radio beacons that can be read on radio direction finders in all weather, radar transponders that appear on radar displays. Beacons can be combined with semaphoric or other indicators to provide important information, such as the status of an airport, by the colour and rotational pattern of its airport beacon, or of pending weather as indicated on a weather beacon mounted at the top of a tall building or similar site; when used in such fashion, beacons can be considered a form of optical telegraphy. Beacons help guide navigators to their destinations. Types of navigational beacons include radar reflectors, radio beacons and visual signals. Visual beacons range from small, single-pile structures to large lighthouses or light stations and can be located on land or on water.
Lighted beacons are called lights. Aerodrome beacons are used to indicate locations of helipads. Handheld beacons are employed in aircraft marshalling, are used by the marshal to deliver instructions to the crew of aircraft as they move around an active airport, heliport or aircraft carrier. Classically, beacons were fires lit at well-known locations on hills or high places, used either as lighthouses for navigation at sea, or for signalling over land that enemy troops were approaching, in order to alert defenses; as signals, beacons were part of a relay league. Systems of this kind have existed for centuries over much of the world; the ancient Greeks called them phryctoriae, while beacons figure on several occasions on the column of Trajan. In the 10th century, during the Arab–Byzantine wars, the Byzantine Empire used a beacon system to transmit messages from the border with the Abbasid Caliphate, across Anatolia to the imperial palace in the Byzantine capital, Constantinople, it was devised by Leo the Mathematician for Emperor Theophilos, but either abolished or radically curtailed by Theophilos' son and successor, Michael III.
Beacons were used in Greece as well, while the surviving parts of the beacon system in Anatolia seem to have been reactivated in the 12th century by Emperor Manuel I Komnenos. In Scandinavia many hill forts were part of beacon networks to warn against invading pillagers. In Finland, these beacons were called vainovalkeat, "persecution fires", or vartiotulet, "guard fires", were used to warn Finn settlements of imminent raids by the Vikings. In Wales, the Brecon Beacons were named for beacons used to warn of approaching English raiders. In England, the most famous examples are the beacons used in Elizabethan England to warn of the approaching Spanish Armada. Many hills in England were named Beacon Hill after such beacons. In England the authority to erect beacons lay wirh the King and was deligated to the Lord High Admiral; the money due for the maintenance of beacons was called Beaconagium and was levied by the sheriff of each county. In the Scottish borders country, a system of beacon fires was at one time established to warn of incursions by the English.
Hume and Eggerstone castles and Soltra Edge were part of this network. The Great Wall of China is a beacon network. In Spain, the border of Granada in the territory of the Crown of Castile had a complex beacon network to warn against Moorish raiders and military campaigns. Vehicular beacons are rotating or flashing lights affixed to the top of a vehicle to attract the attention of surrounding vehicles and pedestrians. Emergency vehicles such as fire engines, police cars, tow trucks, construction vehicles, snow-removal vehicles carry beacon lights; the color of the lamps varies by jurisdiction. Beacons may be constructed with halogen bulbs similar to those used in vehicle headlamps, xenon flashtubes, or LEDs. Incandescent and xenon light sources require the vehicle's engine to continue running to ensure that the battery is not depleted when the lights are used for a prolonged period; the low power consumption of LEDs allows the vehicle's engine to remain turned off while the lights operate nodes.
Beacons and bonfires are used to mark occasions and celebrate events. The Mishna describes a system of fire beacons used by the high court in Jerusalem to communicate the declaration of a new month to Jews in Israel and Babylon. Beacons have allegedly been abused by shipwreckers. An illicit fire at a wrong position would be used to direct a ship against shoals or beaches, so that its cargo could be looted after the ship sank or ran aground. There are, however, no substantiated occurrences of such intentional shipwrecking. In wireless networks, a beacon is a type of frame, sent by the access point to indicate that it is on. Bluetooth based beacons periodically send out a data packet and this could be used by software to identify the beacon location; this is used by indoor navigation and positioning applications. Beaconing is the process; the stations on the network notify the other stations on the ring when they are not receiving the transmissions. Beaconing is used in Token FDDI networks. In Aeschylus' tragedy Agamemnon, a chain of eight beacons manned by so-called lampadóphoroi inform Clytemnestra in Argos, within