Beacons for marking fixed obstacles (SOV) are devices intended to reduce the danger to aircraft by signaling the presence of obstacles.

Tall objects, fixed or mobile, must be marked when they are in certain conditions that could cause a risk of collision in the vicinity of airports and heliports.

Beacons for signaling fixed obstacles must be placed on all high-altitude obstacles such as radio and TV antennas, chimneys, high-tension lines, and any other object with an open or opaque structure in order to signal these objects to aircraft and helicopters. The beacons must mark obstacles both day and night. Beacons for marking fixed obstacles come in different models and types, depending on the obstacle to be marked.

The beacons can have different light intensity depending on the type of terrain, the geographical position and the type of structure where they are placed.

The beacons defined in international standards are generically defined as: low intensity, medium intensity and high luminous intensity beacons:

Then red beacons are used for night signals, and white for night and day signaling. Another type of subdivision is that of the FAA:[1]​.

The production technology of beacons has had a very great evolution in recent years with the use of LED technology, which has replaced the use of incandescent lamps, and this because this technology allows to improve consumption and maintenance costs; In addition, the beacons have a longer average life. Incandescent lamps are still used for low intensity beacons, and for medium and high intensity xenon gas discharge lamps are used.

Beacons for signaling fixed obstacles are placed on all structures that may present a danger to aircraft and helicopters, in the vicinity of airports or heliports as well as on obstacles that protrude into a circulation area for airplanes and helicopters, such as radio antennas, buildings, chimneys, high voltage lines, or any other object with an open or opaque structure.

The standards that define the types of beacons are the ICAO (International Civil Aviation Organization) standards, and the FAA (Federal Aviation Administration) standards.

These standards define the types of beacons and how they must be placed.