Modern Lighthouses
In modern, automated lighthouses:
This system of rotating lenses is often replaced by a very bright light that emits brief Omni directional flashes (concentrating the light in time rather than space). These lights are similar to the aerodrome beacons used to warn aircraft away from tall structures.
In any of these designs an observer, rather than seeing a continuous weak light, sees a brighter light during short time intervals. These instants of bright light are arranged to create a characteristic light pattern specific to the particular lighthouse. For example, for the lighthouse of Scheveningen the time intervals between these instants are alternately 2.5 and 7.5 seconds.
Other design techniques are used to aid the navigator. Lights near to each other are painted in a unique style so they can easily be recognized during the daylight (thus, this marking is called a day mark.) Likewise the time interval of the light (see above) or the color pattern of the lens is varied. Sector lights have particular obstructions in one or more sectors, and a portion of the lantern house may have a red or green filter applied so the navigator gets additional input on which side the ship is approaching from. Modern lighthouses have unique metal attachments so the radar signature of the light is also unique.
Today there are a few keeper-run lighthouses left in existence; the vast majority, however, have been fully automated.
Often in inaccessible locations, modern lighthouses are much more functional and less picturesque buildings; usually they are solar-powered and have a single Flashing light which does not rotate sitting on a steel skeleton tower.
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