This fascinating 1943 U.S. Navy training film shows “How to Signal” using flag hoists, semaphore, and blinker to present morse code messages. The film was produced by F.H. Hargove of the Prior Motion Picture Company in New York and supposedly narrated by “Radcliffe Hall” (like a pseudonym for a radio announcer). A review in “Motor Boating” magazine noted that “the film shows pictorially how to learn the codes in the International Flag, Semaphore and Blinker systems of Communication. Expert signal men in the U.S. service serve as instructors and demonstrate the correct methods of using these three methods. It is designed so that the film may be repeated again and again until the student becomes familiar with the signal flags and positions of the semaphore, and the light flashes of the blinker…”
Flag semaphore is the telegraphy system conveying information at a distance by means of visual signals with hand-held flags, rods, disks, paddles, or occasionally bare or gloved hands. Information is encoded by the position of the flags; it is read when the flag is in a fixed position. Semaphores were adopted and widely used (with hand-held flags replacing the mechanical arms of shutter semaphores) in the maritime world in the 19th century.[citation needed] It is still used during underway replenishment at sea and is acceptable for emergency communication in daylight or, using lighted wands instead of flags, at night.
The use of lights for spelling out messages in Morse code dates back to 1867. With the advent of electric lights in the 1890s, the “blinker light” became an effective tool for signaling. Most widely used by naval ships, blinker lights were essential for merchant ships sailing in wartime convoys and observing radio silence. Blinker has remained a useful backup for merchant vessels, and until the late 1980s deck officers were trained in its use. Usually however, blinker work was done by the Radio Officer.
Beginning in the 1930s, both civilian and military pilots were required to be able to use Morse code, both for use with early communications systems and for identification of navigational beacons which transmitted continuous two- or three-letter identifiers in Morse code. Aeronautical charts show the identifier of each navigational aid next to its location on the map.
Radio telegraphy using Morse code was vital during World War II, especially in carrying messages between the warships and the naval bases of the belligerents. Long-range ship-to-ship communication was by radio telegraphy, using encrypted messages, because the voice radio systems on ships then were quite limited in both their range and their security. Radiotelegraphy was also extensively used by warplanes, especially by long-range patrol planes that were sent out by those navies to scout for enemy warships, cargo ships, and troop ships.
Morse code is a method of transmitting text information as a series of on-off tones, lights, or clicks that can be directly understood by a skilled listener or observer without special equipment. The International Morse Code encodes the ISO basic Latin alphabet, some extra Latin letters, the Arabic numerals and a small set of punctuation and procedural signals (prosigns) as standardized sequences of short and long signals called “dots” and “dashes”, or “dits” and “dahs”, as in amateur radio practice. Because many non-English natural languages use more than the 26 Roman letters, extensions to the Morse alphabet exist for those languages.
Each Morse code symbol represents either a text character (letter or numeral) or a prosign and is represented by a unique sequence of dots and dashes. The duration of a dash is three times the duration of a dot. Each dot or dash is followed by a short silence, equal to the dot duration. The letters of a word are separated by a space equal to three dots (one dash), and the words are separated by a space equal to seven dots. The dot duration is the basic unit of time measurement in code transmission. To increase the speed of the communication, the code was designed so that the length of each character in Morse varies approximately inversely to its frequency of occurrence in English. Thus the most common letter in English, the letter “E”, has the shortest code, a single dot.
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This film is part of the Periscope Film LLC archive, one of the largest historic military, transportation, and aviation stock footage collections in the USA. Entirely film backed, this material is available for licensing in 24p HD and 2k. For more information visit http://www.PeriscopeFilm.com
