A beacon is an intentionally conspicuous device designed to attract attention to a specific location. A common example is the

lighthouse A lighthouse is a tower, building, or other type of physical structure designed to emit light from a system of lamps and lenses and to serve as a beacon for navigational aid, for maritime pilots at sea or on inland waterways. Lighthouses mar ...

, 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

radio beacon In navigation, a radio beacon or radiobeacon is a kind of beacon, a device that marks a fixed location and allows direction-finding equipment to find relative bearing. But instead of employing visible light, radio beacons transmit electromagnet ...

s that can be read on

radio direction finder Direction finding (DF), or radio direction finding (RDF), isin accordance with International Telecommunication Union (ITU)defined as radio location that uses the reception of radio waves to determine the direction in which a radio station ...

s in all weather, and radar transponders that appear on

radar Radar is a detection system that uses radio waves to determine the distance (''ranging''), angle, and radial velocity of objects relative to the site. It can be used to detect aircraft, ships, spacecraft, guided missiles, motor vehicles, w ...

displays. Beacons can also be combined with semaphoric or other indicators to provide important

information Information is an abstract concept that refers to that which has the power to inform. At the most fundamental level information pertains to the interpretation of that which may be sensed. Any natural process that is not completely random ...

, such as the status of an airport, by the colour and rotational pattern of its

airport beacon An aerodrome beacon or rotating beacon or aeronautical beacon is a beacon installed at an airport or aerodrome to indicate its location to aircraft pilots at night. An aerodrome beacon is mounted on top of a towering structure, often a contro ...

, or of pending weather as indicated on a

weather beacon A weather beacon is a beacon that indicates the local weather forecast in a code of colored or flashing lights. Often, a short poem or jingle accompanies the code to make it easier to remember. The beacon is usually on the roof of a tall buil ...

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 An optical telegraph is a line of stations, typically towers, for the purpose of conveying textual information by means of visual signals. There are two main types of such systems; the semaphore telegraph which uses pivoted indicator arms and ...

For navigation

Beacons help guide

navigators A navigator is the person on board a ship or aircraft responsible for its navigation.Grierson, MikeAviation History—Demise of the Flight Navigator FrancoFlyers.org website, October 14, 2008. Retrieved August 31, 2014. The navigator's primar ...

to their destinations. Types of navigational beacons include

reflectors,

radio beacons In navigation, a radio beacon or radiobeacon is a kind of beacon, a device that marks a fixed location and allows direction-finding equipment to find relative bearing. But instead of employing visible light, radio beacons transmit electromagnet ...

, sonic and visual signals. Visual beacons range from small, single-pile structures to large

s or light stations and can be located on land or on water. Lighted beacons are called ''lights''; unlighted beacons are called ''

daybeacon A day beacon (sometimes "daybeacon") is an unlighted nautical sea mark. A signboard identifying it is called a day mark. Day beacons typically mark channels whose key points are marked by lighted buoys. They may also mark smaller navigable rout ...

s''.

Aerodrome beacon An aerodrome beacon or rotating beacon or aeronautical beacon is a beacon installed at an airport or aerodrome to indicate its location to aircraft pilots at night. An aerodrome beacon is mounted on top of a towering structure, often a control ...

s are used to indicate locations of airports and helipads. Handheld beacons are also employed in

aircraft marshalling Aircraft marshalling is visual signalling between ground personnel and pilots on an airport, aircraft carrier or helipad. Activity Marshalling is one-on-one visual communication and a part of aircraft ground handling. It may be as an alternative ...

, 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.

For defensive communications (historical)

Historically, beacons were fires lit at well-known locations on hills or high places, used either as

s for navigation at sea, or for signalling over land that enemy troops were approaching, in order to alert defenses. As signals, beacons are an ancient form of

optical telegraph An optical telegraph is a line of stations, typically towers, for the purpose of conveying textual information by means of visual signals. There are two main types of such systems; the semaphore telegraph which uses pivoted indicator arms and ...

and were part of a

relay league A relay league is a chain of message forwarding stations in a system of optical telegraphs, radio telegraph stations, or riding couriers. Early 19th century methods of this type evolved into the electrical telegraph networks of the mid-to-late 19th ...

. 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 Trajan's Column ( it, Colonna Traiana, la, Columna Traiani) is a Roman triumphal column in Rome, Italy, that commemorates Roman emperor Trajan's victory in the Trajan's Dacian Wars, Dacian Wars. It was probably constructed under the supervision o ...

. In ancient China, sentinels on and near the

Great Wall of China The Great Wall of China (, literally "ten thousand ''li'' wall") is a series of fortifications that were built across the historical northern borders of ancient Chinese states and Imperial China as protection against various nomadic grou ...

used a sophisticated system of daytime smoke and nighttime flame to send signals along long chains of beacon towers. Legend has it that Zhōu Yōu Wáng, king of the

Western Zhou dynasty The Western Zhou ( zh, c=, p=Xīzhōu; c. 1045 BC – 771 BC) was a royal dynasty of China and the first half of the Zhou dynasty. It began when King Wu of Zhou overthrew the Shang dynasty at the Battle of Muye and ended when the Quanrong nomad ...

, played a trick multiple times in order to amuse his often melancholy concubine, ordering beacon towers lit to fool his Marquess and soldiers. But when enemies, led by Marquess of Shen really arrived at the wall, although the towers were lit, no defenders came, leading to Yōu's death and the collapse of the Western Zhou dynasty.

Thucydides Thucydides (; grc, , }; BC) was an Athenian historian and general. His ''History of the Peloponnesian War'' recounts the fifth-century BC war between Sparta and Athens until the year 411 BC. Thucydides has been dubbed the father of "scientifi ...

wrote that during the

Peloponnesian War The Peloponnesian War (431–404 BC) was an ancient Greek war fought between Athens and Sparta and their respective allies for the hegemony of the Greek world. The war remained undecided for a long time until the decisive intervention of th ...

, the Peloponnesians who were in Corcyra were informed by night-time beacon signals of the approach of sixty Athenian vessels from Lefkada. In the 10th century, during the

Arab–Byzantine wars The Arab–Byzantine wars were a series of wars between a number of Muslim Arab dynasties and the Byzantine Empire between the 7th and 11th centuries AD. Conflict started during the initial Muslim conquests, under the expansionist Rashidun an ...

, the

Byzantine Empire The Byzantine Empire, also referred to as the Eastern Roman Empire or Byzantium, was the continuation of the Roman Empire primarily in its eastern provinces during Late Antiquity and the Middle Ages, when its capital city was Constantinopl ...

used a beacon system to transmit messages from the border with the

Abbasid Caliphate The Abbasid Caliphate ( or ; ar, الْخِلَافَةُ الْعَبَّاسِيَّة, ') was the third caliphate to succeed the Islamic prophet Muhammad. It was founded by a dynasty descended from Muhammad's uncle, Abbas ibn Abdul-Muttalib ...

, across

Anatolia Anatolia, tr, Anadolu Yarımadası), and the Anatolian plateau, also known as Asia Minor, is a large peninsula in Western Asia and the westernmost protrusion of the Asian continent. It constitutes the major part of modern-day Turkey. The re ...

to the imperial palace in the Byzantine capital,

Constantinople la, Constantinopolis ota, قسطنطينيه , alternate_name = Byzantion (earlier Greek name), Nova Roma ("New Rome"), Miklagard/Miklagarth (Old Norse), Tsargrad ( Slavic), Qustantiniya (Arabic), Basileuousa ("Queen of Cities"), Megalopolis (" ...

. It was devised by Leo the Mathematician for Emperor Theophilos, but either abolished or radically curtailed by Theophilos' son and successor,

Michael III Michael III ( grc-gre, Μιχαήλ; 9 January 840 – 24 September 867), also known as Michael the Drunkard, was Byzantine Emperor from 842 to 867. Michael III was the third and traditionally last member of the Amorian (or Phrygian) dynasty. ...

. 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 Manuel I Komnenos ( el, Μανουήλ Κομνηνός, translit=Manouíl Komnenos, translit-std=ISO; 28 November 1118 – 24 September 1180), Romanization of Greek, Latinized Comnenus, also called Porphyrogennetos (; "born in the purple"), w ...

. In Scandinavia many

hill fort A hillfort is a type of earthwork used as a fortified refuge or defended settlement, located to exploit a rise in elevation for defensive advantage. They are typically European and of the Bronze Age or Iron Age. Some were used in the post-Roma ...

s were part of beacon networks to warn against invading pillagers. In Finland, these beacons were called ''vainovalkeat'', "persecution fires", or ''vartiotulet'', "guard fires", and were used to warn Finn settlements of imminent raids by the Vikings. In

Wales Wales ( cy, Cymru ) is a Countries of the United Kingdom, country that is part of the United Kingdom. It is bordered by England to the Wales–England border, east, the Irish Sea to the north and west, the Celtic Sea to the south west and the ...

, the

Brecon Beacons The Brecon Beacons ( cy, Bannau Brycheiniog, ) are a mountain range in South Wales. In a narrow sense, the name refers to the range of Old Red Sandstone peaks which lie to the south of Brecon. Sometimes referred to as "the central Beacons" t ...

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 The Spanish Armada (a.k.a. the Enterprise of England, es, Grande y Felicísima Armada, links=no, lit=Great and Most Fortunate Navy) was a Spanish fleet that sailed from Lisbon in late May 1588, commanded by the Duke of Medina Sidonia, an aris ...

. 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

Scottish border The Anglo-Scottish border () is a border separating Scotland and England which runs for between Marshall Meadows Bay on the east coast and the Solway Firth in the west. The surrounding area is sometimes referred to as "the Borderlands". The ...

s 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. In Spain, the border of

Granada Granada (,, DIN 31635, DIN: ; grc, Ἐλιβύργη, Elibýrgē; la, Illiberis or . ) is the capital city of the province of Granada, in the autonomous communities of Spain, autonomous community of Andalusia, Spain. Granada is located at the fo ...

in the territory of the

Crown of Castile The Crown of Castile was a medieval polity in the Iberian Peninsula that formed in 1230 as a result of the third and definitive union of the crowns and, some decades later, the parliaments of the kingdoms of Castile and León upon the accessi ...

had a complex beacon network to warn against Moorish raiders and military campaigns. 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.

Military use (20th-21st century)

Infrared marker

Infrared Infrared (IR), sometimes called infrared light, is electromagnetic radiation (EMR) with wavelengths longer than those of visible light. It is therefore invisible to the human eye. IR is generally understood to encompass wavelengths from around ...

strobes and other infrared beacons have increasingly been used in modern combat when operating at night as they can only be seen through

night vision goggles A night-vision device (NVD), also known as a night optical/observation device (NOD), night-vision goggle (NVG), is an optoelectronic device that allows visualization of images in low levels of light, improving the user's night vision. The dev ...

. As a result, they are often used to mark friendly positions as a form of

IFF In logic and related fields such as mathematics and philosophy, "if and only if" (shortened as "iff") is a biconditional logical connective between statements, where either both statements are true or both are false. The connective is bicon ...

to prevent friendly fire and improve coordination. Soldiers will typically affix them to their helmets 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). Passive markers include IR patches, which reflect infrared light, and

chemlight A glow stick, also known as a light stick, chem light, light wand, light rod, and rave light, is a self-contained, short-term light-source. It consists of a translucent plastic tube containing isolated substances that, when combined, make light ...

s. 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.

On vehicles

Vehicular beacons are rotating or flashing lights affixed to the top of a vehicle to attract the attention of surrounding vehicles and pedestrians.

Emergency vehicle An emergency vehicle is a vehicle used by emergency services. Emergency vehicles typically have specialized emergency lighting and vehicle equipment that allow emergency services to reach calls for service in a timely manner, transport equipment a ...

s 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 with

halogen bulbs A halogen lamp (also called tungsten halogen, quartz-halogen, and quartz iodine lamp) is an incandescent lamp consisting of a tungsten filament sealed in a compact transparent envelope that is filled with a mixture of an inert gas and a small ...

similar to those used in vehicle headlamps, xenon

flashtube A flashtube (flashlamp) is an electric arc lamp designed to produce extremely intense, incoherent, full-spectrum white light for a very short time. A flashtube is a glass tube with an electrode at each end and is filled with a gas that, when tr ...

s, 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.

Other uses

Beacons and

bonfire A bonfire is a large and controlled outdoor fire, used either for informal disposal of burnable waste material or as part of a celebration. Etymology The earliest recorded uses of the word date back to the late 15th century, with the Catho ...

s are also used to mark occasions and celebrate events. Beacons have also allegedly been abused by shipwreckers. An illicit fire at a wrong position would be used to direct a ship against

shoal In oceanography, geomorphology, and geoscience, a shoal is a natural submerged ridge, bank, or bar that consists of, or is covered by, sand or other unconsolidated material and rises from the bed of a body of water to near the surface. It ...

s or

beach A beach is a landform alongside a body of water which consists of loose particles. The particles composing a beach are typically made from rock, such as sand, gravel, shingle, pebbles, etc., or biological sources, such as mollusc shel ...

es, 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, a beacon is a type of

frame A frame is often a structural system that supports other components of a physical construction and/or steel frame that limits the construction's extent. Frame and FRAME may also refer to: Physical objects In building construction *Framing (con ...

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 fiction

Aeschylus Aeschylus (, ; grc-gre, Αἰσχύλος ; c. 525/524 – c. 456/455 BC) was an ancient Greek tragedian, and is often described as the father of tragedy. Academic knowledge of the genre begins with his work, and understanding of earlier Greek ...

' tragedy '' Agamemnon'', a chain of eight beacons staffed by so-called ''lampadóphoroi'' inform Clytemnestra in

Argos Argos most often refers to: * Argos, Peloponnese, a city in Argolis, Greece ** Ancient Argos, the ancient city * Argos (retailer), a catalogue retailer operating in the United Kingdom and Ireland Argos or ARGOS may also refer to: Businesses * ...

, within a single night's time, that

Troy Troy ( el, Τροία and Latin: Troia, Hittite language, Hittite: 𒋫𒊒𒄿𒊭 ''Truwiša'') or Ilion ( el, Ίλιον and Latin: Ilium, Hittite language, Hittite: 𒃾𒇻𒊭 ''Wiluša'') was an ancient city located at Hisarlik in prese ...

has just fallen under her husband king Agamemnon's control, after a famous ten years siege. In

J. R. R. Tolkien John Ronald Reuel Tolkien (, ; 3 January 1892 – 2 September 1973) was an English writer and philology, philologist. He was the author of the high fantasy works ''The Hobbit'' and ''The Lord of the Rings''. From 1925 to 1945, Tolkien was ...

's high fantasy novel, ''

The Lord of the Rings ''The Lord of the Rings'' is an epic high-fantasy novel by English author and scholar J. R. R. Tolkien. Set in Middle-earth, intended to be Earth at some time in the distant past, the story began as a sequel to Tolkien's 1937 children's boo ...

'', a series of beacons alerts the entire realm of

Gondor Gondor is a fictional kingdom in J. R. R. Tolkien's writings, described as the greatest realm of Man (Middle-earth), Men in the west of Middle-earth at the end of the Third Age. The third volume of ''The Lord of the Rings'', ''The Return of the ...

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 Gondor is a fictional kingdom in J. R. R. Tolkien's writings, described as the greatest realm of Men in the west of Middle-earth at the end of the Third Age. The third volume of ''The Lord of the Rings'', ''The Return of the King'', is largely ...

. In

Peter Jackson Sir Peter Robert Jackson (born 31 October 1961) is a New Zealand film director, screenwriter and producer. He is best known as the director, writer and producer of the ''Lord of the Rings'' trilogy (2001–2003) and the ''Hobbit'' trilogy ( ...

's film 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.

In retail

Beacons are sometimes used in retail to send digital coupons or invitations to customers passing by.

Types

Infrared beacon

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 in

robotics Robotics is an interdisciplinary branch of computer science and engineering. Robotics involves design, construction, operation, and use of robots. The goal of robotics is to design machines that can help and assist humans. Robotics integrat ...

and in

Combat Identification Identification, friend or foe (IFF) is an identification system designed for command and control. It uses a transponder that listens for an ''interrogation'' signal and then sends a ''response'' that identifies the broadcaster. IFF systems usual ...

(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.

Sonar beacon

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.

References

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