A beacon is an intentionally conspicuous device designed to attract attention to a specific location. 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 radio beacons that can be read on radio direction finders 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, we ...

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, 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 lighthouses or light stations and can be located on land or on water. Lighted beacons are called ''lights''; unlighted beacons are called '' daybeacons''. Aerodrome beacons 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 alternat ...

, 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 lighthouses 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 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 19t ...

. Systems of this kind have existed for centuries over much of the world. The ancient Greeks called them ''

phryctoriae Phryctoria ( el, φρυκτωρία) was a semaphore system used in Ancient Greece. The ''phryctoriae'' were towers built on selected mountaintops so that one tower (''phryctoria'') would be visible to the next tower (usually 20 miles away). The t ...

'', 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 Dacian Wars. It was probably constructed under the supervision of the architect Apo ...

. 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 gro ...

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 nom ...

, 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 The Marquess of Shen ( Chinese: , p ''Shēnhóu''; d. 771 BCE) was a Qiang ruler of Shen during China’s Zhou dynasty. A vassal state of the Zhou, Shen state covered the area of modern-day Nanyang in Henan. One of the Marq ...

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 " scienti ...

wrote that during the Peloponnesian War, the Peloponnesians who were in

Corcyra Corfu (, ) or Kerkyra ( el, Κέρκυρα, Kérkyra, , ; ; la, Corcyra.) is a Greek island in the Ionian Sea, of the Ionian Islands, and, including its small satellite islands, forms the margin of the northwestern frontier of Greece. The isl ...

were informed by night-time beacon signals of the approach of sixty Athenian vessels from

Lefkada Lefkada ( el, Λευκάδα, ''Lefkáda'', ), also known as Lefkas or Leukas ( Ancient Greek and Katharevousa: Λευκάς, ''Leukás'', modern pronunciation ''Lefkás'') and Leucadia, is a Greek island in the Ionian Sea on the west coast of G ...

. In the 10th century, during the Arab–Byzantine wars, 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 ...

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 Leo the Mathematician, the Grammarian or the Philosopher ( grc-gre, Λέων ὁ Μαθηματικός or ὁ Φιλόσοφος, ''Léōn ho Mathēmatikós'' or ''ho Philósophos''; – after January 9, 869) was a Byzantine philosopher and ...

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 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 country that is part of the United Kingdom. It is bordered by England to the east, the Irish Sea to the north and west, the Celtic Sea to the south west and the Bristol Channel to the south. It had a population in ...

, 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 The Elizabethan era is the epoch in the Tudor period of the history of England during the reign of Queen Elizabeth I (1558–1603). Historians often depict it as the golden age in English history. The symbol of Britannia (a female personific ...

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 of the United Kingdom, 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 Castle, Hume 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. 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 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 device, night vision goggles. As a result, they are often used to mark friendly positions as a form of Identification friend or foe, IFF to prevent friendly fire and improve coordination. Soldiers will typically affix them to their Combat helmet, 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 chemlights. 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 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 with Automotive lamp types, halogen bulbs similar to those used in vehicle headlamps, xenon flashtubes, or light-emitting diode, 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 bonfires are also used to mark occasions and celebrate events. Beacons have also allegedly been abused by Wrecking (shipwreck), 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 historically substantiated occurrences of such intentional shipwrecking. In wireless networks, a Electric beacon#IEEE 802.11 Wi-Fi beacons, beacon is a type of Frame (networking), 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 positioning system, 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

In Aeschylus' tragedy ''Oresteia, Agamemnon'', a chain of eight beacons staffed by so-called ''lampadóphoroi'' inform Clytemnestra in Argos, Peloponnese, Argos, within a single night's time, that Troy has just fallen under her husband king Agamemnon's control, after a famous Trojan War, ten years siege. In J. R. R. Tolkien's high fantasy novel, ''The Lord of the Rings'', a Warning beacons of Gondor, 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 (Middle-earth), Rohan or Belfalas. In Peter Jackson's The Lord of the Rings: The Return of the King, 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 and in Combat 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.

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

{{Authority control Beacons,