Flag semaphore

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A US Navy crewman signals the letter 'U' using flag semaphore during an underway replenishment exercise (2005) US Navy 051129-N-0685C-007 Quartermaster Seaman Ryan Ruona signals with semaphore flags during a replenishment at sea.jpg
A US Navy crewman signals the letter 'U' using flag semaphore during an underway replenishment exercise (2005)

Flag semaphore (from the Greek σῆμα, sema, meaning sign and φέρω, phero, meaning to bear; altogether the sign-bearer) 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. [1] 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.[ citation needed ]

Contents

Contemporary semaphore flag system

The current flag semaphore system uses two short poles with square flags, which a signal person holds in different positions to signal letters of the alphabet and numbers. The signaller holds one pole in each hand, and extends each arm in one of eight possible directions. Except for in the rest position, the flags do not overlap. The flags are colored differently based on whether the signals are sent by sea or by land. At sea, the flags are colored red and yellow (the Oscar flag), while on land, they are white and blue (the Papa flag). Flags are not required; their purpose is to make the characters more obvious.[ citation needed ]

Characters

The following 30 semaphore characters are presented as they would appear when facing the signalperson:

Numbers can be signaled by first signaling "Numerals". Letters can be signaled by first signaling "J".

The sender uses the "Attention" signal to request permission to begin a transmission. The receiver uses a "Ready to receive" signal not shown above to grant permission to begin the transmission. The receiver raises both flags vertical overhead and then drops them to the rest position, once only, to grant permission to send. The sender ends the transmission with the "Ready to receive" signal. The receiver can reply with the "Attention" signal. At this point, sender and receiver change places.

Origin

Flag semaphore originated in 1866 as a handheld version of the optical telegraph system of Home Riggs Popham used on land, and its later improvement by Charles Pasley. The land system consisted of lines of fixed stations (substantial buildings) with two large, moveable arms pivoted on an upright member. Such a system was inconvenient to install on board a ship. Flag semaphore provided an easy method of communicating ship-to-ship or ship-to-shore when the distances were not too great. According to Alexander J. Field of Santa Clara University, "there is evidence" that Popham based his telegraph on the French coastal stations used for ship-to-shore communication. [2] Many of the codepoints of flag semaphore match those of the Foy-Breguet electrical telegraph, also descended from the French optical telegraph. Although based on the optical telegraph, by the time flag semaphore was introduced the optical telegraph had been entirely replaced by the electrical telegraph some years previously. [3]

Japanese semaphore

The combination used for o ("O") Shou Qi Xin Hao o.svg
The combination used for オ ("O")

The Japanese merchant marine and armed services have adapted the flag semaphore system to the Japanese language. [4] Because their writing system involves a syllabary of about twice the number of characters in the Latin alphabet, most characters take two displays of the flags to complete; others need three and a few only one. The flags are specified as a solid white square for the left hand and a solid red one for the right. The display motions chosen are not like the "rotary dial" system used for the Latin alphabet letters and numbers; rather, the displays represent the angles of the brush strokes used in writing in the katakana syllabary and in the order drawn. For example, the character for "O" [オ], which is drawn first with a horizontal line from left to right, then a vertical one from top to bottom, and finally a slant between the two; follows that form and order of the arm extensions. It is the right arm, holding the red flag, which moves as a pen would, but in mirror image so that the observer sees the pattern normally. As in telegraphy, the katakana syllabary is the one used to write down the messages as they are received. Also, the Japanese system presents the number 0 by moving flags in a circle, and those from 1 through 9 using a sort of the "rotary dial" system, but different from that used for European languages.

Practical use in communication

Semaphore flags are also sometimes used as means of communication in the mountains where oral or electronic communication is difficult to perform. Although they do not carry flags, the Royal Canadian Mounted Police officers have used hand semaphore in this manner. Some surf-side rescue companies, such as the Ocean City, Maryland Beach Patrol, use semaphore flags to communicate between lifeguards. [5] The letters of the flag semaphore are also a common artistic motif. One enduring example is the peace symbol, adopted by the Campaign for Nuclear Disarmament in 1958 from the original logo created by a commercial artist named Gerald Holtom from Twickenham, London. [6] Holtom designed the logo for use on a protest march on the Atomic Weapons Establishment at Aldermaston, near Newbury, England. On 4 April 1958, the march left Trafalgar Square for rural Berkshire, carrying Ban the Bomb placards made by Holtom's children making it the first use of the symbol. Originally, it was purple and white and signified a combination of the semaphoric letters N and D, standing for "nuclear disarmament," circumscribed by a circle. [7]

Along with Morse code, flag semaphore is currently used by the Navy and also continues to be a subject of study and training for young people of Scouts. In a satirical nod to the flag semaphore's enduring use into the age of the Internet, on April Fools' Day 2007 the Internet Engineering Task Force standards organization outlined the Semaphore Flag Signaling System, a method of transmitting Internet traffic via a chain of flag semaphore operators. [8]

The album cover for the Beatles' 1965 album Help! was originally to have portrayed the four band members spelling "help" in semaphore, but the result was deemed aesthetically unpleasing, and their arms were instead positioned in a meaningless but aesthetically pleasing arrangement. [9]

The second episode in the second series of Monty Python's Flying Circus depicted famous stories retold using various communication systems, including Wuthering Heights in semaphore.

See also

Related Research Articles

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The Baudot code[bodo] is an early character encoding for telegraphy invented by Émile Baudot in the 1870s, It was the predecessor to the International Telegraph Alphabet No. 2 (ITA2), the most common teleprinter code in use until the advent of ASCII. Each character in the alphabet is represented by a series of five bits, sent over a communication channel such as a telegraph wire or a radio signal. The symbol rate measurement is known as baud, and is derived from the same name.

Code System of rules to convert information into another form or representation

In communications and information processing, code is system of rules to convert information—such as a letter, word, sound, image, or gesture—into another form, sometimes shortened or secret, for communication through a communication channel or storage in a storage medium (source?). An early example is the invention of language, which enabled a person, through speech, to communicate what they saw, heard, felt, or thought to others. But speech limits the range of communication to the distance a voice can carry, and limits the audience to those present when the speech is uttered. The invention of writing, which converted spoken language into visual symbols, extended the range of communication across space and time.

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Electrical telegraph An early system for transmitting text over wires

An electrical telegraph was a point-to-point text messaging system, used from the 1840s until better systems became widespread. It used coded pulses of electric current through dedicated wires to transmit information over long distances. It was the first electrical telecommunications system, the most widely used of a number of early messaging systems called telegraphs, devised to send text messages more rapidly than written messages could be sent. This system allowed for communication to occur without the necessity of physical transportation. Prior to this, beacons, smoke signal, flag semaphore, and optical telegraphs used visual signals to communicate over distances of land.

Morse code Transmission of language with brief pulses

Morse code is a method used in telecommunication to encode text characters as standardized sequences of two different signal durations, called dots and dashes or dits and dahs. Morse code is named after Samuel Morse, an inventor of the telegraph.

Semaphore usually refers to flag semaphore. It may also refer to;

Telegraphy Long distance transmission of text without the physical exchange of an object

Telegraphy is the long-distance transmission of textual messages where the sender uses symbolic codes, known to the recipient, rather than a physical exchange of an object bearing the message. Thus flag semaphore is a method of telegraphy, whereas pigeon post is not. Ancient signalling systems, although sometimes quite extensive and sophisticated as in China, were generally not capable of transmitting arbitrary text messages. Possible messages were fixed and predetermined and such systems are thus not true telegraphs.

Wireless telegraphy method of communication

Wireless telegraphy or radiotelegraphy is transmission of telegraph signals by radio waves; Before about 1910 when radio became dominant, the term wireless telegraphy was also used for various other experimental technologies for transmitting telegraph signals without wires, such as electromagnetic induction, and ground conduction telegraph systems.

SOS is a Morse code distress signal, used internationally, that was originally established for maritime use. In formal notation SOS is written with an overscore line, to indicate that the Morse code equivalents for the individual letters of "SOS" are transmitted as an unbroken sequence of three dots / three dashes / three dots, with no spaces between the letters. In International Morse Code three dots form the letter "S" and three dashes make the letter "O", so "S O S" became a common way to remember the order of the dots and dashes.

Optical telegraph Communication along a chain of towers using mechanically operated paddles or shutters

An optical telegraph is a line of stations, typically towers, for the purpose of conveying textual information by means of visual signals. There are two main types of such systems; the semaphore telegraph which uses pivoted indicator arms and conveys information according to the direction the indicators point, and the shutter telegraph which uses panels that can be rotated to block or pass the light from the sky behind to convey information.

Optical communication communication at a distance using light to carry information

Optical communication, also known as optical telecommunication, is communication at a distance using light to carry information. It can be performed visually or by using electronic devices. The earliest basic forms of optical communication date back several millennia, while the earliest electrical device created to do so was the photophone, invented in 1880.

A telegraph code is one of the character encodings used to transmit information by telegraphy. Morse code is the most well known such code. Telegraphy usually refers to the electrical telegraph, but telegraph systems using the optical telegraph were in use before that. A code consists of a number of code points, each corresponding to a letter of the alphabet, a numeral, or some other character. In codes intended for machines rather than humans, code points for control characters, such as carriage return, are required to control the operation of the mechanism. Each code point is made up of a number of elements arranged in a unique way for that character. There are usually two types of element, but more element types were employed in some codes not intended for machines. For instance, American Morse code had about five elements, rather than the two of International Morse Code.

Flag signals can mean any of various methods of using flags or pennants to send signals. Flags may have individual significance as signals, or two or more flags may be manipulated so that their relative positions convey symbols. Flag signals allowed communication at a distance before the invention of radio and are still used especially in connection with ships.

International Code of Signals Maritime communication method

The International Code of Signals (ICS) is an international system of signals and codes for use by vessels to communicate important messages regarding safety of navigation and related matters. Signals can be sent by flaghoist, signal lamp ("blinker"), flag semaphore, radiotelegraphy, and radiotelephony. The International Code is the most recent evolution of a wide variety of maritime flag signalling systems.

Hydraulic telegraph

A hydraulic telegraph is either of two different hydraulic-telegraph telecommunication systems. The earliest one was developed in 4th-century BC Greece, while the other was developed in 19th-century AD Britain. The Greek system was deployed in combination with semaphoric fires, while the latter British system was operated purely by hydraulic fluid pressure.

In computer networking, Semaphore Flag Signaling System (SFSS) is a humorous proposal to carry Internet Protocol (IP) traffic by semaphores. Semaphore Flag Signaling System was initially described in RFC 4824, an April Fools RFC issued by the Internet Engineering Task Force edited by J. Hofmueller, et al. and released on April Fool's Day 2007. It is one of several April 1 RFCs.

Maritime flag signalling, generally flaghoist signalling, is the principal means other than radio by which ships communicate to each other or to shore. Virtually all signalling by non-naval vessels is now organized under the International Code of Signals, which specifies a standard set of flags and codes. Naval vessels generally use an extended set of flags and their own codes. This article will touch on the historical development of maritime flag signalling.

Naval flag signalling covers various forms of flag signalling, such as semaphore or flaghoist, used by various navies; distinguished from maritime flag signalling by merchant or other non-naval vessels or flags used for identification.

Wigwag (flag signals) Method of flag signaling

Wigwag is an historical form of flag signaling that passes messages by waving a single flag. It differs from flag semaphore in that it uses one flag rather than two, and the symbols for each letter are represented by the motion of the flag rather than its position. The larger flag and its motion allow messages to be read over greater distances than semaphore. Messages could be sent at night using torches instead of flags.

References

  1. "History of Semaphore" (PDF). Royal Navy Communications Branch Museum/Library. Retrieved 16 May 2020.
  2. Alexander J. Field, "French optical telegraphy, 1795–1855: Hardware, software, administration", Technology and Culture, vol. 35, no. 2, pp. 315–347, April 1994.
  3. Signals at Sea, Information sheet no 104, Library and Information Services, The National Museum: Royal Navy: Portsmouth, accessed and archived 26 October 2019.
  4. 1 2 "The Flag Signalling System in Japan". 22 July 2011. Archived from the original on 22 July 2011. Retrieved 10 October 2013.
  5. "Ocean City Beach Patrol Semaphore Alphabet" (PDF). Oceancitymd.gov.
  6. Bayley, Stephen (6 April 2008). "Fifty years on, the CND logo is the ultimate design for life". The Guardian. London. Retrieved 6 April 2008.
  7. Kathryn Westcott (20 March 2008). "World's best-known protest symbol turns 50". BBC News. He [Gerald Holtom] considered using a Christian cross motif but, instead, settled on using letters from the semaphore – or flag-signalling – alphabet, super-imposing N (uclear) on D (isarmament) and placing them within a circle symbolising Earth.
  8. Hofmueller, Jogi; Bachmann, Aaron; Zmoelnig, IOhannes (1 April 2007). The Transmission of IP Datagrams over the Semaphore Flag Signaling Syst em (SFSS). IETF. doi: 10.17487/RFC4824 . RFC 4824 . Retrieved 20 March 2010.
  9. Freeman, Robert (2003). The Beatles: A Private View. NY: Barnes & Noble. p. 62. ISBN   978-1-59226-176-5.CS1 maint: ref=harv (link)