Semaphore Signal Reference
See how a message breaks down into letters, digits, and mode-shift signs in flag semaphore, and estimate how long it takes to send.
Signal plan
| Digit | Numeral-shift letter |
|---|---|
| 7 | G |
| 3 | C |
Two flags, eight positions
Flag semaphore signals letters by holding two flags, one in each hand, in one of eight positions spaced 45° apart around the body — think of a clock face with a position at every other hour mark. Each letter is a unique pairing of a left-flag position and a right-flag position, which is why a trained signaler can send text as fast as they can move their arms.
Because there are no separate positions left over for digits, the system reuses the alphabet itself: a “Numerals” sign tells the receiver that the next letters should be read as numbers (A=1 through I=9, J=0), and a “Letters” sign switches back. It's the same kind of trick a Morse operator uses with prosigns, just done with flags instead of dots and dashes.
Frequently Asked Questions
How are numbers sent in flag semaphore?
Semaphore has no separate flag positions for digits. Instead, a signaler sends a "Numerals" sign to switch into number mode, after which the letters A through J stand in for the digits 1 through 9 and 0, in alphabetical order. A "Letters" sign switches back.
Why does the tool count "mode shifts"?
Every time a message switches between a run of letters and a run of digits, the signaler has to send an extra Numerals or Letters sign. Counting those shifts gives a realistic total for how many signs actually have to be sent, not just how many characters are in the message.
Where does the signaling rate come from?
Semaphore speed varies a lot with experience, so the rate (signs per minute) is something you choose rather than a single fixed fact — a beginner might manage a much slower pace than a well-drilled signaler. Adjust it to estimate your own or a group's realistic sending time.
Does this show the exact flag position for every letter?
No — reproducing the precise two-flag position for all 26 letters accurately from a written description is error-prone, so this reference focuses on the parts of the system that are simple and verifiable: the numeral substitution and message timing. For the visual letter positions, a standard illustrated semaphore chart is the reliable source.
Educational tool only. Signaling-rate estimates are approximate and depend entirely on the signaler's skill and conditions.