Semaphore Flags is the system for 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 early 19th century. Semaphore signals were used, for example, at the Battle of Trafalgar. This was the period in which the modern naval semaphore system was invented. This system uses hand-held flags. 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.
Wig-wag signalling (or wigwagging) uses one flag for signalling, in a method similar to semaphore, but by opening and closing the sign, the Morse code equivalent of dots and dashes are used to convey the message. It was used in US Civil War times. A signal corpsman commonly stood on a platform about 6–10 feet off the ground, signaling to other units. The bright orange red and white flag made a primary target for the enemy.
The newer flag semaphore system uses two short poles with square flags, which a signalman holds in different positions to signal letters of the alphabet and numbers. The signalman holds one pole in each hand, and extends each arm in one of eight possible directions. Except for in the rest position, the flags cannot overlap. The flags are coloured differently based on whether the signals are sent by sea or by land. At sea, the flags are coloured red and yellow (the Oscar flag), while on land, they are white and blue (the Papa flag). Flags are not required, they just make the characters more obvious.
The following semaphore characters are presented as one would face the signalman:
Numbers can be signaled by first signaling "Numerals". To change back to letters, simply signal "J". (See discussion)
The Japanese merchant marine and armed services have adapted the flag semaphore system to the Japanese language, as shown in Japanese here. 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.
Along with Morse code, the flag semaphore has seen use as a method of communication amongst adventurous children, as portrayed in the Swallows and Amazons series of children's books by Arthur Ransome.
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.
Also many surf-side rescue companies, such as the Ocean City Maryland Beach Patrol, use semaphore flags to communicate between lifeguards. 
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, which is a combination of the semaphoric letters N and D, standing for "nuclear disarmament," circumscribed by a circle. Famously, the album cover for The Beatles' 1965 album Help! was to have portrayed the four band members spelling "HELP" in semaphore with their arms, though the result was deemed aesthetically unpleasing, and the band's arms were instead positioned in a meaningless but aesthetically pleasing arrangement for the final version of the album art.
In a nod to the flag semaphore's enduring use into the age of the Internet, a satirical proposal by the Internet Engineering Task Force standards organization in 2007 outlined a method of transmitting Internet traffic via a chain of flag semaphore operators.
- Ransome, Arthur (1933). Winter Holiday. Jonathan Cape. Check date values in:
- OCBP Site, |title=Ocean City MAryland Semaphore Alphabet | http://oceancitymd.gov/Recreation_and_Parks/Beach_Patrol/semaphore.html
- Kathryn Westcott (2008-03-20). "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.
- Freeman, Robert. The Beatles: A Private View. NY: Barnes & Noble. p. 62. ISBN 1-59226-176-0.CS1 maint: ref=harv (link)
- Hofmueller, Jogi; Bachmann, Aaron; Zmoelnig, IOhannes (1 April 2007). The Transmission of IP Datagrams over the Semaphore Flag Signaling System (SFSS). IETF. RFC 4824. https://tools.ietf.org/html/rfc4824. Retrieved March 20, 2010.
bar:Semafor cs:Semafor (abeceda) da:Semafor de:Winkeralphabet es:Semáforo (comunicación) fr:Alphabet sémaphore id:Semaphore is:Merkjasending it:Alfabeto semaforico lt:Semaforinės vėliavėlės nl:Semafooralfabet ja:手旗信号 no:Semafor pl:Alfabet semaforowy ru:Семафорная азбука sr:Семафорска сигнализација sv:Semaforalfabetet tl:Semaporong watawat zh:旗語