Abeacon is an intentionally conspicuous device designed to attract attention to aspecific location. A common example is thelighthouse, which draws attention to a fixed point that can be used to navigate around obstacles or into port. More modern examples include a variety ofradio beacons that can be read onradio direction finders in all weather, andradar transponders that appear onradar displays.
Beacons can also be combined with semaphoric or other indicators to provide importantinformation, such as the status of an airport, by the colour and rotational pattern of itsairport beacon, or of pending weather as indicated on aweather beacon mounted at the top of a tall building or similar site. When used in such fashion, beacons can be considered a form ofoptical telegraphy.
Beacons help guidenavigators to their destinations. Types of navigational beacons includeradar reflectors,radio beacons, sonic and visual signals. Visual beacons range from small, single-pile structures to largelighthouses or light stations and can be located on land or on water. Lighted beacons are calledlights; unlighted beacons are calleddaybeacons.Aerodrome beacons are used to indicate locations of airports and helipads.[1]
In the United States, a series of beacons were constructed across the country in the 1920s and 1930s to help guide pilots deliveringair mail. They were placed about 25 miles apart from each other, and included large concrete arrows with accompanying lights to illuminate them.[2]
Handheld beacons are also employed inaircraft marshalling, and are used by the marshal to deliver instructions to the crew of aircraft as they move around an active airport, heliport or aircraft carrier.[3]
Historically, beacons were fires lit at well-known locations on hills or high places, used either aslighthouses fornavigation at sea, or for signalling over land that enemy troops were approaching, in order to alert defenses. As signals, beacons are an ancient form ofoptical telegraph and were part of arelay league.
Systems of this kind have existed for centuries over much of the world. The ancient Greeks called themphryctoriae, while beacons figure on several occasions on thecolumn of Trajan.
In imperial China, sentinels on and near theGreat Wall of China used a sophisticated system of daytime smoke and nighttime flame to send signals along long chains of beacon towers.[4]
Legend has it thatKing You of Zhou played a trick multiple times in order to amuse his often melancholy concubine, ordering beacon towers lit to fool his vassals and soldiers. But when enemies, led by theMarquess of Shen really arrived at the wall, although the towers were lit, no defenders came, leading to King Yōu's death and the collapse of the Western Zhou dynasty.[4][5][6] However, in reality the Great Wall did not exist until long after King You's death.[7]
Thucydides wrote that during thePeloponnesian War, thePeloponnesians who were inCorcyra were informed by night-time beacon signals of the approach of sixty Athenian vessels fromLefkada.[8]
In the 10th century, during theArab–Byzantine wars, theByzantine Empire used abeacon system to transmit messages from the border with theAbbasid Caliphate, acrossAnatolia to theimperial palace in the Byzantine capital,Constantinople. It was devised byLeo the Mathematician for EmperorTheophilos, but either abolished or radically curtailed by Theophilos' son and successor,Michael III.[9] Beacons were later 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 EmperorManuel I Komnenos.[9]
In the Nordic countries,hill forts and beacon networks were important for warning against invasions.[10] In Sweden and Finland, these beacons, known asvårdkasar orbötar, formed an extensive coastal warning system from the Late Iron Age and through the Middle Ages. Beacons were strategically placed on high ground for visibility, constructed fromtar-rich wood to ensure bright flames. They were mentioned in medieval laws likeUpplandslagen and described by Swedish writerOlaus Magnus in 1555 as tools for mobilising armed defenders during crises.[10] In Finland, similar beacons calledvainovalkeat ("persecution fires") orvartiotulet ("guard fires") warned settlements of raids.[11]
InWales, theBrecon Beacons were named for beacons used to warn of approaching English raiders. In England, the most famous examples are the beacons used inElizabethan England to warn of the approachingSpanish Armada. Many hills in England were named Beacon Hill after such beacons. In England the authority to erect beacons originally lay with the King and later was delegated to theLord High Admiral. The money due for the maintenance of beacons was calledBeaconagium and was levied by the sheriff of each county.[12] In theScottish 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.[13]
In Spain, the border ofGranada in the territory of theCrown of Castile had a complex beacon network to warn against Moorish raiders and military campaigns.[14] Due to the progressive advance of the borders throughout the process of the Reconquista, the entire Spanish geography is full of defensive lines of castles, towers and fortifications, visually connected to each other, which served as fortified beacons. Some examples are the Route of the Vinalopó castles or the distribution of the castles in Jaén.
In later centuries, advancements in technology, such as thetelegraph, rendered beacon systems obsolete for rapid communication.[15] The use of such beacons transitioned from practical communication to symbolic and ceremonial roles,[16] where the lighting of beacons was repurposed to mark significant national events.
Beacons were lit across the United Kingdom to celebrate Queen Victoria'sDiamond Jubilee in 1897, Queen Elizabeth II'sPlatinum Jubilee in 2022,[17] and to commemorate events such as the 70th anniversary ofVE Day, and the 80th anniversary of theD-Day landings in 2024.[16]
South Korea maintains a daily ceremonial beacon lighting atNamsan Beacon Mound inSeoul, where visitors witness a reenactment of the traditionalbongsu ceremony, which historically signaled emergencies.[18]
Infrared strobes and other infrared beacons have increasingly been used in modern combat when operating at night as they can only be seen throughnight vision goggles. As a result, they are often used to mark friendly positions as a form ofIFF to prevent friendly fire and improve coordination. Soldiers will typically affix them to theirhelmets or other gear so they are easily visible to others using night vision including other infantry, ground vehicles, and aerial platforms (drones, helicopters, planes, etc.).[19]
Passive markers include IR patches, which reflect infrared light, andchemlights. The earliest such beacons were often IR chemlights taped to helmets.
As time went on, more sophisticated options began to emerge with electronically powered infrared strobes with specific mounting solutions for attaching to helmets or load bearing equipment. These strobes may have settings which allow constant on or strobes of IR light, hence the name.[20]
Advancements in near-peer technology, however, present risk since if friendly units can see the strobe with night vision so could enemies with night vision capabilities. As a result, some in the American military have stressed that efforts should be made to improve training regarding light discipline (IR and visible) and other means of reducing a unit's visible signature.[19]
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, ambulances, police cars, tow trucks, construction vehicles, and snow-removal vehicles carry beacon lights.
The color of the lamps varies by jurisdiction; typical colors are blue and/or red for police, fire, and medical-emergency vehicles; amber for hazards (slow-moving vehicles, wide loads, tow trucks, security personnel, construction vehicles, etc.); green for volunteer firefighters or for medical personnel, and violet for funerary vehicles. Beacons may be constructed withhalogen bulbs similar to those used in vehicleheadlamps, xenonflashtubes, orLEDs.[21] 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.
Beacons have also allegedly been abused byshipwreckers. An illicit fire at a wrong position would be used to direct a ship againstshoals orbeaches, so that its cargo could be looted after the ship sank or ran aground. There are, however, no historically substantiated occurrences of such intentional shipwrecking.
In wireless networks, abeacon is a type offrame which is sent by the access point (or WiFi router) 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 typically used byindoor navigation and positioning applications.[22]
Beaconing is the process that allows a network to self-repair network problems. The stations on the network notify the other stations on the ring when they are not receiving the transmissions. Beaconing is used in Token ring and FDDI networks.
InAeschylus' tragedyAgamemnon,[23] a chain of eight beacons staffed by so-calledlampadóphoroi informClytemnestra inArgos, within a single night's time, thatTroy has just fallen under her husband king Agamemnon's control, after a famousten years siege.
InJ. R. R. Tolkien'shigh fantasy novel,The Lord of the Rings, aseries of beacons alerts the entire realm ofGondor when the kingdom is under attack. These beacon posts were staffed by messengers who would carry word of their lighting to eitherRohan orBelfalas.[24] InPeter Jackson'sfilm adaptation of the novel, the beacons serve as a connection between the two realms of Rohan and Gondor, alerting one another directly when they require military aid, as opposed to relying on messengers as in the novel.
The Beacon was an influential Caribbean magazine published in Trinidad in the 1930s.New Beacon Books was the first Caribbean publishing house in England, founded in London in 1966, was named after theBeacon journal.[25]
Beacons are sometimes used in retail to send digital coupons or invitations to customers passing by.[26][27]
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An infrared beacon (IR beacon) transmits a modulated light beam in the infrared spectrum, which can be identified easily and positively. A line of sight clear of obstacles between the transmitter and the receiver is essential. IR beacons have a number of applications inrobotics and inCombat Identification (CID).
Infrared beacons are the key infrastructure for the Universal Traffic Management System (UTMS) in Japan. They perform two-way communication with travelling vehicles based on highly directional infrared communication technology and have a vehicle detecting capability to provide more accurate traffic information.[28]
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A sonar beacon is an underwater device which transmits sonic or ultrasonic signals for the purpose of providing bearing information. The most common type is that of a rugged watertight sonar transmitter attached to a submarine and capable of operating independently of the electrical system of the boat. It can be used in cases of emergencies to guide salvage vessels to the location of a disabled submarine.[29]
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