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International Code of Signals (Overview)

Last modified: 2000-10-27 by phil nelson
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International Code of Signals (Overview)

The International Code of Signals was first drafted in 1855 by the British Board of Trade and subsequently published in 1857 as a means of maritime communications. The original publication showed 17,000 signals using 18 flags, part of which was specific to the United Kingdom and another part that contained universal signals to be used by all nations. Adopted by most sea-faring nations, the system was revised in 1932 to include seven languages: English, French, German, Italian, Japanese, Spanish, and Norwegian.

The Fourth Assembly of the Intergovernmental Maritime Consultative Organization revised the code in 1965 which became effective on January 1, 1969. This revision added Russian and Greek to the languages already included and adopted a new radiotelephone code. Each signal has a complete meaning.
Jorge Candeias, 31 August 1999


I asked a Flagmakers firm ("Industrial Velera Marsal S.A.") and they make 3 sizes measuring: 1.98x2.41 m, 1.37x1.68 m and 0.76x0.91 m, which they assure are "official". I don´t find any proportions kept at the 3 sizes. They are close to 8-10, but a little more "squared" than that.

Maritime letter flags, as far as I know, go back to Sir Home Popham, who published "Telegraphic Signals or Marine Vocabulary" in 1800, with a larger version in 1803, and another expanded edition in 1812.

This was used by Nelson to signal his fleet before the beginning of the battle of Trafalgar, the 21 of october, 1805, the famous message: "ENGLAND EXPECTS THAT EVERY MAN WILL DO HIS DUTY". Certainly those flags were 1-1 in proportions and can be seen in several books.

After many manuals and codes, the actual international signal flags developed from Captain Frederick Marryat´s "Code of Signals for the Merchant Service".

This actual international code is what we need to find out if it has construction sheets.

In Whitney Smith´s 1975 book, page 86, letter flags are drawn in prop. 8-10.
Jose C. Alegria, 25 August 1999

I am not a specialist of signal flags (Album des Pavillons presents all national flags, ensigns and markings at sea, but not signal flags) yet I had a look at the technical spoecifications of French Navy and British Royal Navy : signal flags have the following measures (in cm).
French Navy 198 : 244
137 : 168
76 : 91
British Navy 183 : 229
114 : 152
102 : 122
61 : 76
46 : 53
30 : 38
Armand Noel du Payrat, 25 August 1999

Here are the correct proportions for the International Ship Code Flags:
  • Letters A & B-1:1.5 (swallowtailed)
  • Letters C - Z (& the US Navy's set of 10 numerical square flags)-1:1 (square)
  • The 10 ISCF numerical-& the code/answering-pennants-5:9 (tapered at fly)
  • The 4 substituters (repeaters), the books-on-board (white with a blue reader), & the PROMPT (yellow/green/yellow-new!!) pennants-7:11 (triangular).
Robert Lloyd Wheelock, 25 August 1999

In Flags at Sea, Timothy Wilson wrote; "The most common sizes for signal flags of the International Code nowadays (1986) are: 78 inches by 96 inches, 54 inches by 66 inches, and 30 inches by 36 inches."

The sizes offered in a current catalogue are (all in inches): 9x12, 12x18, 18x21, 24x30, 30x36, 43x54, 48x72.

Marryat suggested that his flags should be 6 feet by 8 feet, with pennants 4 feet by 18 feet.
David Prothero, 28 August 1999

The US Navy page on signal flags, also shows what look like 1:1 proportions. Although the depiction of the "Romeo" flag looks to me like the cross is too narrow, so use your best judgment on reliability of the other representations. The page also shows USN vs. international meanings of individual flags, for those interested.
Joseph McMillan, 31 August 1999

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