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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 mark ...
, 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 electromagne ...
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, weat ...
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.


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
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, weat ...
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 electromagne ...
, sonic and visual signals. Visual beacons range from small, single-pile structures to large
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 mark ...
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 route ...
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 contro ...
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 alternativ ...
, 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
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 mark ...
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 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 group ...
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 noma ...
, 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 Ma ...
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 " scientif ...
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 t ...
, 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 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 and ...
, 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 to the imperial palace in the Byzantine capital, Constantinople. 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 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), Latinized Comnenus, also called Porphyrogennetos (; "born in the purple"), was a Byzantine emperor ...
. 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-Rom ...
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 2 ...
, 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" th ...
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 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 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. In Spain, the border of
Granada Granada (,, DIN: ; grc, Ἐλιβύργη, Elibýrgē; la, Illiberis or . ) is the capital city of the province of Granada, in the autonomous community of Andalusia, Spain. Granada is located at the foot of the Sierra Nevada mountains, at the c ...
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 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 bicond ...
to prevent friendly fire and improve coordination. Soldiers will typically affix them to their
helmets A helmet is a form of protective gear worn to protect the head. More specifically, a helmet complements the skull in protecting the human brain. Ceremonial or symbolic helmets (e.g., a policeman's helmet in the United Kingdom) without protec ...
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 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 ...
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 similar to those used in vehicle
headlamp A headlamp is a lamp attached to the front of a vehicle to illuminate the road ahead. Headlamps are also often called headlights, but in the most precise usage, ''headlamp'' is the term for the device itself and ''headlight'' is the term f ...
s, 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 A light-emitting diode (LED) is a semiconductor device that emits light when current flows through it. Electrons in the semiconductor recombine with electron holes, releasing energy in the form of photons. The color of the light (cor ...
. 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 o ...
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 shells ...
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 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 mode ...
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 (co ...
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

In
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 In Greek mythology, Agamemnon (; grc-gre, Ἀγαμέμνων ''Agamémnōn'') was a king of Mycenae who commanded the Greeks during the Trojan War. He was the son, or grandson, of King Atreus and Queen Aerope, the brother of Menelaus, the hus ...
'', a chain of eight beacons staffed by so-called ''lampadóphoroi'' inform
Clytemnestra Clytemnestra (; grc-gre, Κλυταιμνήστρα, ''Klytaimnḗstrā'', ), in Greek mythology, was the wife of Agamemnon, king of Mycenae, and the twin sister of Helen of Troy. In Aeschylus' ''Oresteia'', she murders Agamemnon – said by E ...
in Argos, within a single night's time, that
Troy Troy ( el, Τροία and Latin: Troia, Hittite: 𒋫𒊒𒄿𒊭 ''Truwiša'') or Ilion ( el, Ίλιον and Latin: Ilium, Hittite: 𒃾𒇻𒊭 ''Wiluša'') was an ancient city located at Hisarlik in present-day Turkey, south-west of Çan ...
has just fallen under her husband king Agamemnon's control, after a famous ten years siege. In J. R. R. Tolkien's
high fantasy High fantasy, or epic fantasy, is a subgenre of fantasy defined by the epic nature of its setting or by the epic stature of its characters, themes, or plot. Brian Stableford, ''The A to Z of Fantasy Literature'', (p. 198), Scarecrow Press, P ...
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 bo ...
'', 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 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 larg ...
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 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 interdisciplinarity, 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 human ...
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.


See also

*
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 contro ...
* Beacon mode service * Beacon School *
Belisha beacon A Belisha beacon is an amber-coloured globe lamp atop a tall black and white striped pole, marking pedestrian crossings of roads in the United Kingdom, Ireland, and in other countries historically influenced by Britain such as Hong Kong, Malta ...
*
Emergency locator beacon An emergency locator beacon is a radio beacon, a portable battery powered radio transmitter, used to locate airplanes, vessels, and persons in distress and in need of immediate rescue. Various types of emergency locator beacons are carried by air ...
*
Emergency position-indicating radiobeacon station An Emergency Position-Indicating Radio Beacon (EPIRB) is a type of emergency locator beacon for commercial and recreational boats, a portable, battery-powered radio transmitter used in emergencies to locate boaters in distress and in need of ...
(ELTs, PLBs & EPIRBs) *
iBeacon iBeacon is a protocol developed by Apple and introduced at the Apple Worldwide Developers Conference in 2013. Various vendors have since made iBeacon-compatible hardware transmitters – typically called beacons – a class of Bluetoo ...
* Lantern *
Leading lights Leading lights (also known as range lights in the United States) are a pair of light beacons used in navigation to indicate a safe passage for vessels entering a shallow or dangerous channel; they may also be used for position fixing. At night ...
*
Lighthouse of Alexandria The Lighthouse of Alexandria, sometimes called the Pharos of Alexandria (; Ancient Greek: ὁ Φάρος τῆς Ἀλεξανδρείας, contemporary Koine ), was a lighthouse built by the Ptolemaic Kingdom of Ancient Egypt, during the re ...
*
Milestone A milestone is a numbered marker placed on a route such as a road, railway, railway line, canal or border, boundary. They can indicate the distance to towns, cities, and other places or landmarks; or they can give their position on the rou ...
/
Kilometric point A milestone is a numbered marker placed on a route such as a road, railway line, canal or boundary. They can indicate the distance to towns, cities, and other places or landmarks; or they can give their position on the route relative to s ...
* Polaris * Strobe beacon *
Time ball A time ball or timeball is a time-signalling device. It consists of a large, painted wooden or metal ball that is dropped at a predetermined time, principally to enable navigators aboard ships offshore to verify the setting of their marine chron ...
*
Trail blazing Trail blazing or way marking is the practice of marking paths in outdoor recreational areas with signs or markings that follow each other at certain, though not necessarily exactly defined, distances and mark the direction of the trail. A blaz ...
* Warning light (disambiguation) *
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 ...
*
Web beacon A web beaconAlso called web bug, tracking bug, tag, web tag, page tag, tracking pixel, pixel tag, 1×1 GIF, or clear GIF. is a technique used on web pages and email to unobtrusively (usually invisibly) allow checking that a user has accessed s ...


References

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