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 beacon
s that can be read on radio direction finder
s in all weather, and radar transponder
s that appear on radar
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 airport 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
Beacons help guide navigators
to their destinations. Types of navigational beacons include radar
reflectors, radio beacons
, sonic and visual signals. Visual beacons range from small, single-pile structures to large lighthouse
s or light stations and can be located on land or on water. Lighted beacons are called ''lights''; unlighted beacons are called ''daybeacon
s''. Aerodrome beacon
s are used to indicate locations of airports and helipads.
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.
For defensive communications (historical)
Historically, beacons were fires lit at well-known locations on hills or high places, used either as lighthouse
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
and were part of a relay league
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 ancient China, sentinels on and near the Great Wall of China
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, 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.
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 Scandinavia many hill fort
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.
, 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 Scottish border
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
in the territory of the Crown of Castile
had a complex beacon network to warn against Moorish raiders and military campaigns.
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
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
s, xenon flashtube
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 nodes.
Beacons and bonfire
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
s or beach
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
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
''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.
' tragedy ''Agamemnon
'', a chain of eight beacons manned by so-called ''lampadóphoroi'' inform Clytemnestra
, within a single night's time, that Troy
has just fallen under her husband king Agamemnon's control, after a famous ten years siege
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 manned by messengers who would carry word of their lighting to either Rohan
In Peter Jackson
'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.
Beacons are sometimes used in retail to send digital coupons or invitations to customers passing by.
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
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.
A contemporary military use of an Infrared beacon is reported in Operation Acid Gambit
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.The ELAC SBE distress sonar beacon
* Aerodrome beacon
* Beacon mode service
* Beacon School
* Belisha beacon
* Emergency locator beacon
* Emergency position-indicating radiobeacon station (ELTs, PLBs & EPIRBs)
* Leading lights
* Lighthouse of Alexandria
* Milestone/Kilometric point
* Strobe beacon
* Time ball
* Trail blazing
* Warning light (disambiguation)
* Weather beacon
* Web beacon