Cute Young Brunette Girl With French Braid Hairstyle Posing At The Signal Lamp

Naval usage
Aldis lamps were pioneered by the British Royal Navy in the late 19th century, and continue to be used through the present day on naval vessels. They provide handy, secure communications during periods of radio silence as well as other times and were particularly useful for convoys operating during the Battle of the Atlantic. There were several types. Some signal lamps were mounted on the mastheads of ships, some small hand-held versions were also used ('The Aldis lamp') and other more powerful ones were mounted on pedestals. These larger ones used a carbon arc lamp as their light source with a diameter of 20 inches (50 cm). These could be used to signal to the horizon, even in conditions of bright sunlight. Although it was originally thought that it was only possible to communicate by line-of-sight, in practice it was possible to illuminate cloud bases both during the night and day which allowed for communication beyond the horizon. A maximum transmission rate possible by using flashing lights is no more than 14 wpm.
They have a secondary function as simple spotlights.
The idea of flashing dots and dashes from a lantern was first put in to practice by Captain, later Vice Admiral, Philip Colomb in 1867. His original code, which the Navy used for seven years, was not identical with Morse, but Morse code was eventually adopted with the addition of several special signals. Flashing lights were the second generation of signaling in the Royal Navy, after the flag signals most famously used to spread Nelson's rallying-cry before the Battle of Trafalgar.