FOGHORNS AND RADIO SIGNALS

Many lighthouses are equipped with a horn to help guide ships sailing in foggy weather. These foghorns, which make their sound by quickly releasing compressed air, can be heard for distances of up to 13 km (8 mi).

Ship captains can determine their position by identifying distinctive combinations of long and short horn blasts specific to each lighthouse. Some lighthouses are also equipped with radio beacons that transmit Morse-code radio signals.

These radio signals, which are distinguished by short (dot) and long (dash) combinations, have a range of up to 320 km (200 mi).

Lighthouse

Lighthouse, structure from which light is projected at night, or which serves as a marker by day, to guide ships sailing in coastal waters.

Lighthouses are constructed at important points on a coastline, at entrances to harbors and estuaries, on rocky ledges or reefs, on islands, and even in the water. Lighthouses help identify a ship’s location, warn ships of potential hazards, and notify them that land is near.

Lighthouses differ from smaller beacons in that a lighthouse includes living quarters for a lighthouse keeper. Today, however, most lighthouses use automatic electric lights that do not require a full-time resident operator.

The first lighthouses were built long before the time of Christ. The earliest known reference to a lighthouse dates back to 1200 bc. This reference appeared in the Iliad, Homer’s Greek epic poem. The first onshore beacons that were used to guide ships were bonfires.

Eventually, bonfires were replaced with iron baskets filled with burning wood or coal and suspended on long poles. It was not until the 18th century that these baskets were replaced by oil or gas lanterns.

In the early to mid-20th century, electric beacons replaced oil and gas lanterns.