S in Morse code
The nineteenth letter of the alphabet
The letter S in Morse code is three dots, ..., spoken di-di-dit. All three are short and evenly spaced, so at 18 WPM the whole letter lasts about 333 milliseconds, a third of a second. S is best known as the first and last letter of SOS. Count with care: two dots make I, four make H, and three dots followed by a dash make V.
... (dot dot dot)
“di-di-dit”dot dot dot
3 elements · 3 dots · 5 units
Hear it at your speed (WPM)
333 ms at 18 WPM
S at a glance
- Morse code
- ...
- Said as
- di-di-dit
- Elements
- 3
- Length
- 5 units
- At 18 WPM
- 333 ms
- Koch order
- 6 of 41Then N
- NATO word
- Sierra
- Frequency in English
- 6.3%7th of 26
How S sounds and how to send it
S is five units long: three dots of one unit each, with a one-unit silence between them. There is no long tone anywhere in it, so it reads as a quick, even triple. At the site's speed of 18 WPM one unit is 66.7 milliseconds, which puts the letter at about 333 milliseconds.
Straight key:
tap three times, keeping the taps and the gaps equal.
Bug:
on a semi-automatic key, pushing the paddle to the side sets a pendulum rocking that makes evenly timed dots by itself, so S is a short push that you release after the third dot.
Paddles:
with paddles and an electronic keyer you work the dot paddle and the keyer spaces the dots for you.
Written down, S is three periods in a row. Flashed with a light, it is three short flashes with dark gaps as long as the flashes themselves.
Telling S from I, H, 5 and V
The dot-only characters form a ladder: . is E, .. is I, ... is S, .... is H and ..... is the digit 5. Nothing but the count separates them, so the usual mistake is hearing three dots as two or four. Wait for the letter gap before you write anything down.
Put a dash after the three dots and S becomes V, ...-, so a long tone right after the third dot changes the letter. Swap all three dots for dashes and you get O, ---, the letter S frames in the middle of SOS.
The sound-alike drill has a set for E, I, S, H and 5 that plays them against each other until the counts stick. You can also find S beside every other letter on the full alphabet chart.
Hear it
- E.
- I..
- H....
S in SOS and the end-of-work signal
SOS is S, O and S keyed as one signal with no letter gaps, ...---..., which makes it 23 units long, about 1.5 seconds at 18 WPM. German radio regulations introduced it on April 1, 1905. The International Radiotelegraph Convention, signed on November 3, 1906, made it the international standard from July 1, 1908.
The pattern was chosen as a sound, not as an abbreviation; "save our souls" was fitted to the letters later. SOS in Morse code plays the call at its true spacing, and how to signal SOS covers sending it with a light, a whistle or by tapping.
S also opens the signal that closes a contact. ITU-R M.1677-1 gives end of work as ...-.-, the three dots of S run straight into K, and operators write it SK, or sometimes VA.
Hear it
- SOS...---...
- SK...-.-
Remembering S: su-per-man and si-si-si
Say su-per-man with every syllable equally light, or the Spanish si-si-si, and you have the rhythm of S: three short beats and no long one. Because there is nothing to stress, the only thing to learn is the number three.
S is the seventh most common letter in English text, at about 6.3% of letters, so once the triple sticks you will hear it in almost every line of plain-language Morse.
Characters to compare
Close to S in sound, so the likeliest mix-ups.
- S minus its last dot: I, dot dot
- S plus a dot: H, dot dot dot dot
- S plus a dash: V, dot dot dot dash
- S with dots and dashes swapped: O, dash dash dash
- S with its 1st dot as a dash: D, dash dot dot
- S with its 2nd dot as a dash: R, dot dash dot
Which one did you hear?
Listen, then pick or type the one you heard.
Try S in a word
Tap S yourself
Press for a dot, hold for a dash. Space works too.
- Send
- ...
- Yours
- Nothing yet
Questions about S.
What is the SOS symbol in Morse code?
SOS is three dots, three dashes and three dots sent as one unbroken signal, ...---..., with no gaps between the letters. At 18 WPM it lasts about 1.5 seconds. It is the international distress signal, kept for real danger to life or property.
What is V in Morse code?
V is ...-, three dots and a dash, said di-di-di-dah. It starts exactly like S, so a listener who hears three dots has to wait: if a dash follows before the letter gap, the letter is V, not S.
What do three dots mean in Morse code?
Three dots with a letter gap after them are the letter S. If a fourth dot follows without a gap the letter is H, and if a dash follows it is V. Three dots, three dashes and three dots run together are SOS.
What are the Morse code letters and numbers?
International Morse gives each of the 26 letters and the 10 digits its own pattern of dots and dashes. Letters use one to four elements and every digit uses five. The alphabet chart shows them all with sound.