A beacon is an intentionally conspicuous device designed to attract attention to a specific location.
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 lighthouses or light stations and can be located on land or on water. Lighted beacons are called lights; unlighted beacons are called daybeacons.
For defensive communications
Classically, 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 telegraphy, and were part of a relay league.
Systems of this kind have existed for centuries over much of the world. In Scandinavia many hill forts were part of beacon networks to warn against invading pillagers. 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 the Scottish borders country a system of beacon fires were at one time established to warn of incursions by the English. Hume, Eggerstone castle and Soltra Edge were part of this network.
Vehicular beacons are typically 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 lights are used for tow trucks, security personnel, and construction vehicles. Beacons may be constructed with traditional incandescent bulbs, xenon flashtubes, or LEDs.. 20th century light sources required the vehicle’s engine to continue running to ensure that the battery would not be depleted when the lights were used for more than a few hours. The energy efficiency of the LED source allows the vehicle's engine to remain turned off while the light flashes.
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