Signal lamp

A signal lamp (sometimes called an Aldis lamp or a Morse lamp) is a visual signaling device for optical communication by flashes of a lamp, typically using Morse code. The idea of flashing dots and dashes from a lantern was first put into practice by Captain Philip Howard Colomb, of the Royal Navy, in 1867. Colomb's design used limelight for illumination, and his original code was not the same as Morse code. During World War I, German signalers used optical Morse transmitters called Blinkgerät, with a range of up to 8 km (5 miles) at night, using red filters for undetected communications. Modern signal lamps produce a focused pulse of light, either by opening and closing shutters mounted in front of the lamp, or by tilting a concave mirror. They continue to be used to the present day on naval vessels and for aviation light signals in air traffic control towers, as a backup device in case of a complete failure of an aircraft's radio. Signal lamps were pioneered by the Royal Navy in the late 19th century. They were the second generation of signalling in the Royal Navy, after the flag signals most famously used to spread Nelson's rallying-cry, "England expects that every man will do his duty", before the Battle of Trafalgar. The idea of flashing dots and dashes from a lantern was first put into practice by Captain, later Vice Admiral, Philip Howard Colomb, of the Royal Navy, in 1867. Colomb's design used limelight for illumination. His original code was not identical to Morse code, but the latter was subsequently adopted. Another signalling lamp was the Begbie lamp, a kerosene lamp with a lens to focus the light over a long distance. During the trench warfare of World War I when wire communications were often cut, German signals used three types of optical Morse transmitters, called Blinkgerät, the intermediate type for distances of up to 4 km (2.5 miles) in daylight and of up to 8 km (5 miles) at night, using red filters for undetected communications. In 1944 Arthur Cyril Webb Aldis patented a small hand-held design, which featured an improved shutter.