beacon

A beacon is a signaling device designed to attract attention and convey information at a distance. The term comes from the Old English beacen, meaning sign or signal. Beacons have been used since ancient times to warn of danger, mark routes, or guide travelers.

Historically beacons were fires or smoke signals placed on hilltops or coastlines to relay messages quickly across long distances. The concept evolved into durable structures such as lighthouses that provide light and sound to aid navigation at sea.

In modern contexts beacons fall into physical and electronic categories. Physical beacons include lighthouses and other navigational aids; radio beacons such as non-directional beacons used in aviation. Electronic and wireless beacons include Bluetooth Low Energy devices that periodically transmit identifiers to nearby devices for location-based services.

Beacons are used for navigation, safety, asset tracking, and emergency signaling. In computing and networking, beacons can also refer to periodic signals that indicate presence, synchronize systems, or trigger events in distributed systems.