A lighthouse is a tower near the coast or next to it, although sometimes it is located in the sea some distance from the coast, which is located at the site of the shipping routes of the vessels and provides on top of a powerful lamp, whose light is used as a guide.
The lamp has Fresnel lens whose number, width, color separation and varies according to each lighthouse. When the lighthouse in the darkness is in operation, the lamp emits beams of light through the lens, rotating 360 degrees.
From the sea the boats not only see the light of the lighthouse, which warns of the proximity of the coast, but also identified the ranges and colors of the light beams, so that they can recognize the face of what the coast are found.
Modern satellite navigation systems like GPS, have downplayed the lights but still useful (safety) for night navigation and allows the verification of positioning on the navigation chart.
In restricted waters such as channels of access are still navigating by reference to buoys and lights on earth as it is not rowed since the relevant geographic position as well as the relative positions of the surrounding dangers.
At the entrance to ports, built by the Romans used to have high towers that served as a imitation of the famous lighthouse of Alexandria and erected by Ptolemy Lake remembering which pyres of apotheosis, was composed of truncated pyramids placed on a decrease in others. Sometimes also used as beacons colossal figures. This was the Colossus of Rhodes [1].
During the Middle Ages, the headlights were not subjected to any further except that its setting was sometimes remarkable. In the seventeenth century were not yet headlights bonfires of wood rather than burning coal in weirs or beautiful lanterns lamps encased in glass in 1782 until the engineer Teulère replaced as imperfect means of parabolic reflectors for lamps [2].
In the nineteenth century, the illumination of the headlights was a huge step with the invention by the Fresnel lens of stairs, consisting of a glass core surrounded by an ordinary series of thin rings whose profile is so we all have the same focus at the same time with Arago invented Frsnel twisted concentric lamps that produce an intense light equivalent to many lamps Jail [3].
In the past, the headlights have a keeper who used to live in the lighthouse, and had to deal with the maintenance and cleaning of light, especially light installations. Currently, lighthouses still in use are mostly operated automatically and remotely monitored.
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