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A beacon is an intentionally conspicuous device designed to attract attention to a Geodetic datum. A common example is the lighthouse, which draws attention to a fixed point that can be used to navigate around obstacles or into port. More modern examples include a variety of that can be read on radio direction finders in all weather, and Transponder that appear on radar displays.
Beacons can also 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 aerodrome 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.
In the United States, a series of beacons were constructed across the country in the 1920s and 1930s to help guide pilots delivering air mail. They were placed about 25 miles apart from each other, and included large concrete arrows with accompanying lights to illuminate them.
Handheld beacons are also employed in aircraft 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.
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 imperial China, sentinels on and near the Great Wall used a sophisticated system of daytime smoke and nighttime flame to send signals along long chains of beacon towers.
Legend has it that King 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 the Marquess 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. (1999). 9781139053709 ISBN 9781139053709 However, in reality the Great Wall did not exist until long after King You's death.
Thucydides wrote that during the Peloponnesian War, the Peloponnese who were in Corcyra were informed by night-time beacon signals of the approach of sixty Athenian vessels from Lefkada. Thucydides, Peloponnesian War, 3.80
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 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 Emperor Manuel I Komnenos.
In the Nordic countries, Hillfort and beacon networks were important for warning against invasions. In Sweden and Finland, these beacons, known as vårdkasar or böte, 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 from tar-rich wood to ensure bright flames. They were mentioned in medieval laws like Upplandslagen and described by Swedish writer Olaus Magnus in 1555 as tools for mobilising armed defenders during crises. In Finland, similar beacons called vainovalkeat ("persecution fires") or vartiotulet ("guard fires") warned settlements of raids.
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 originally lay with the King and later was delegated 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 country, a system of beacon fires was at one time established to warn of incursions by the English. Hume Castle and Eggerstone castles and Soltra Edge were part of this 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.Els almogávers a la frontera amb el sarrains en el segle XIV. Maria Teresa Ferrer 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.
Beacons were lit across the United Kingdom to celebrate Queen Victoria's Diamond Jubilee in 1897, Queen Elizabeth II's Platinum Jubilee in 2022, and to commemorate events such as the 70th anniversary of VE Day, and the 80th anniversary of the D-Day landings in 2024.
South Korea maintains a daily ceremonial beacon lighting at Namsan Beacon Mound in Seoul, where visitors witness a reenactment of the traditional bongsu ceremony, which historically signaled emergencies.
Passive markers include IR patches, which reflect infrared light, and . 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.
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.
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 with halogen bulbs similar to those used in vehicle , xenon , 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.
In wireless networks, a beacon is a type of frame 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 by indoor navigation and positioning applications.
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.
In J. R. R. Tolkien's high fantasy novel, The Lord of the Rings, a series of beacons alerts the entire realm of Gondor when the kingdom is under attack. These beacon posts were staffed by messengers who would carry word of their lighting to either Rohan or Belfalas. In Peter Jackson's , 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.
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.
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