Maritime Signal Flags

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Signal flags have long been used for communication between ships at sea. In time, mariners developed a standard set of flags and pennants for this purpose. Used singly or in simple combinations, these flags have various special meanings. But they can also be used to spell out complete words and phrases. (The "yankee" and "zulu" flags at the top of this page are used to indicate that what follows is such a literal message.)

After seeing Jim Croft's interesting collection of information on flags, I made a game of it. Click on the button below and you'll be given a message to read.

The flags are displayed vertically in "hoists". In a real exchange between ships, the receiving ship displays the "answer" pennant (at the dip) after each hoist is seen. Each word in a phrase is displayed in a separate hoist. The number of flags available is limited, though, so a single word may be split between multiple hoists.

Since a ship normally carries only one set of flags, the same flag obviously can't be used more than once in a hoist. This limitation is ameliorated to some extent by using "substitute" pennants. Use of the third substitute pennant, for example, indicates that the third flag or pennant in the hoist is to be repeated at the substitute's position. A substitute pennant refers to the same type of character, either letter or number, as immediately precedes it. Thus in a hoist with the flags "A", "2", "C", "4", and "second substitute", the substitute refers to the second number and the translation is "A2C44".

I am not an expert on the use of signal flags; if you see something here that's incorrect or that could be improved, please let me know. I'd like to learn more about the history of signal flags, too, so any references would be appreciated. Have fun!

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