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Signal Flags

Last modified: 2000-10-07 by phil nelson
Keywords: signal flags | international | signal code | quarantine | blue peter |
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The Peabody Essex Museum in Salem (Massachusetts, USA) has put together a WWW page on the history of signal flags. It is well illustrated with colour images of various signal systems, maritime paintings, and has short explanatory texts.You can find the page at

According to this site, the International Code of Signals we use now, was published in 1857 (originally drafted two years earlier).

Jan Oskar Engene, 1996 March 22

The International Signal Code

All signal code flags are square, although A and B are broadly swallowtailed. The colours are as follows:

  • A = vertically divided, white on hoist, blue on fly.
  • B = red
  • C = horizontally divided, blue-white-red-white-blue, ratio 1:1:1:1:1
  • D = horizontally divided, yellow-blue-yellow, ratio 1:2:1
  • E = horizontally divided, blue over red
  • F = white field, with red square rotated 45 o on to its corner, extending to the edges of the flag
  • G = vertically divided (from hoist) yellow-blue-yellow-blue-yellow-blue
  • H = vertically divided white on hoist and red on fly.
  • I = yellow field, small black circle in centre
  • J = horizontally equally divided blue-white-blue
  • K = vertically divided, yellow on hoist, blue on fly
  • L = quartered, first and fourth yellow, second and third black.
  • M = blue field, white saltire-style cross
  • N = chequered, four rows and four columns, alternating blue and white, beginning with blue in the upper hoist
  • O = diagonally divided, yellow in the lower hoist, red in the upper fly.
  • P = blue field, small white square centred on it
  • Q = yellow; the quarantine flag
  • R = red field, yellow cross
  • S = white field, small blue square centred on it
  • T = vertically equally divided, red-white-blue from hoist to fly
  • U = quartered, first and fourth red, second and third white
  • V = white field, red saltire-style cross
  • W = blue field, white square centred on it, small red square centred in the white
  • X = white field, blue cross
  • Y = diagonally striped, stripes rising from lower hoist to upper fly, yellow-red-yellow-red-yellow-red-yellow-red-yellow-red
  • Z = diagonally quartered, yellow in upper sector, black along hoist, red in lower sector, blue in fly sector.

Signal Flags in Combinations

Ship signal flags can also be gouped in pairs to make new combinate meanings. Here is a list I took from Dictionaire Complet et Illustré Petit Larousse, 1996

  • NC      I'm in danger
  • ED      Your help signal was understood
  • KP      Tow me to port
  • FO      I'm standing by you
  • PM      Follow me
  • IR      Stay at large
  • JG      I'm astray
  • NA      Navigation prohibited
  • KN      I can't tow you

Aside from that, the flag for "shipwreck" is plain black. Somehow I fail to imagine what is the use of hoisting a flag on a drowning ship, but... :-\

Antonio Martins, 1998 February 03

The international signal code was elaborated by OMCI in 1965. They presented signals of 1 letter (emergency or frequent use), 2 letters, 3 letters (medical part), with possibly 1, 2, or 3 numeral completives. You can find them in all major hydrographic offices. in the book I have, proportions showed are (approx): 4 / 3 for letter flags, 16 / 3 for numeral pennants, 5 / 4 for substitutes. The black flag does not appear in it any more.

Armand Noel du Payrat, 1998 February 14

Blue Peter

I have been searching for info on the origins of signalling flags - those used predominantly by the shipping/naval community, I assume the origin is British Royal Navy in the Napoleonic timeframe, but that is at best a guess.

There appears to be controversy over the source of the name 'Blue Peter' - some say its from 'Blue repeater' (but that is a different flag), and others say its from the French 'partir' - used when leaving harbour.
Rob Bedford, 1999 January 15 and 1999 January 18

Introduced into Royal Navy in the 1750's, as a blue flag with six white balls. Soon after 1756 the white balls were replaced by a white square. "By Rodney's time (c1780) this flag at the mainmast head had become the signal to recall everyone to his ship." Perrin, "British Flags". 1803. "She has had Blue Peter's flag flying at the fore as a signal for sailing." First entry in Oxford English Dictionary. 1862. "The Blue Peter at the foremast head was flying as a summons to the hands on shore to come aboard." Only other entry in OED.

"Blue Repeater"? Looks plausible, but the sense doesn't fit the use. In a signal by flag hoist, there is no such thing as a "repeater" is there? If you want to repeat a flag you use a substitute, and it is described by a number, not a colour.

French "partir"? Haven't heard that one before. I expect some one in France can tell us if they have a name for this flag; "P" in the International Code.

The explanation may lie as much as in the word "blue", as in the word "peter". It is not a blue flag. It is a blue and white flag. Why call it a "blue peter", when there are no "red peters", or "white peters"? I think that it is a corruption of the early official description of the flag, which was the heraldic term "blue pierced white".

The first public commercial code (there were earlier private semi-commercial codes, as used for instance by the East India Company) was the "Code of Signals for the Merchant Service". This was produced in 1817 by Captain Fredrick Marryat, R.N. as the result of problems experienced by ships of the Royal Navy trying to communicate with merchant ships in convoy. It was a numerary code for British ships only, based upon the "Signal Book for Ships of War", which had been introduced for all ships in the Royal Navy in 1799. It was modified with words more appropriate for commercial use.

Ships of other countries began using it, and in 1854, when the 12th edition was published, it was re-titled, "The Universal Code of Signals".

In 1855 the British "Board of Trade" decided that maritime signals needed to be regulated, and authorised the publication in 1857, of the "Commercial Code of Signals". This was an alphabetical code and a considerable improvement on Marryat's numerary code.

It was re-named the "International Code" in about 1870, and revised in 1901 and 1934. There was another revision to the Code in 1969 but I think mainly to sections dealing with electronic communication.
David Prothero, 1999 January 20

It may have been derived from a plain blue flag that was commonly used in the early 1700's, by the Dutch, Danish and Swedish navies, as a signal that a ship was preparing to sail. It is unlikely to have been used by the Royal Navy, as a plain blue flag was a command flag flown by an admiral of the blue squadron. In the 19th century when the "blue flag with a white square in the centre" had been widely adopted as a signal of departure, it was commonly known as "Blue Peter" in north European languages, but not in French or Spanish.

Marryat (who was also a novelist and wrote "Mr Midshipman Easy") based his 1817 Merchant Service Code on Naval Codes that had been introduced in about the middle of the 18th century, and gradually improved over the following years. Before that time signals had been made with ordinary ensigns, jacks, pennants and standards, rather than flags designed specifically for the purpose. The position in the ship where the flag was hung, was as significant as the flag itself. The early codes were often two flag hoists, based on a table of messages set in a grid, the upper flag indicating the column of the grid and the lower flag the row. These were replaced by proper numerary codes with each one of ten flags, indicating one of the numbers 0 to9. Additional flags were used to indicate beginning and end of messages, substitutes, hundreds and thousands.

The flags could only indicate a number which related to a pre-determined message, and the next improvement was the vocabulary code. In this system numbers could indicate a single word or phrase, so that sentences could be built up from scratch. Finally the number of flags was increased so that most letters of the alphabet could be signalled separately in order to build-up uncommon words. The numerary code continued in use alongside the vocabulary code, as it was a more efficient way of signalling commonly used messages.

Marryat's code was numerary and used the Union Jack as one of the signal flags. This had the result that British merchant ships were able to fly the Union Jack as part of a signal hoist, but not as an ensign or jack. The Admiralty objected to this and in the fourth edition of Marryat's code published in 1826, a white bordered Union Jack replaced the Union Jack. Some interesting terms used in correspondence between Marryat and the Admiralty; "New Signal Jack" was the UJ with a white border; "His Majesty's Jack" was the UJ; and "the National Red Ensign", was the plain Red Ensign, which at the time was still a naval flag as well as the merchant flag.

One peculiarity of the 1857 code introduced by the Board of Trade, was that although it had flags representing letters, there were only 18 of them, B to W and no vowels; so that objectionable three and four letter words could not be signalled by rude sailors.

The 1901 code introduced the full set of letters and the 1934 code added numbers.
David Prothero, 1999 February 03

I found a reference to the Blue Peter in the book Naval Ceremonies, Customs, and Traditions 4th Ed. by William P. Mack and Royal W. Connell. It reads:

BLUE PETER. A flag, "blue pierced with white," was used in the British Navy from 1777 as a general recall flag. In a quarter of a century the term "blue peter" was used by all to designate this flag. Civilians knew its significance, for merchant ships and convoys in the French wars would not sail until the escorting man-of-war hoisted the blue peter for passengers to come aboard.

There is on record a historic piece of doggerel, autographed "Emma," written when Nelson sailed in 1801:

Silent grief and sad forebodings
(Lest I ne'er should see him more)
Fill my heart when gallant Nelson
Hoists blue peter at the fore.

The "Blue Peter" was at the time of the War of 1812 flown at the fore preparatory to sailing.
Mike White, 22 October 1999

See also: Vexillology

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