SOS in Morse Code

SOS in Morse code is three dots, three dashes, three dots: ... --- ... It is sent as one continuous signal, not as the three separate letters S, O and S.

The pattern

• Three dots: short signals, one unit each.
• Three dashes: long signals, three units each.
• Three dots again: the short signal returns.

As a prosign, the nine marks run together with only the one-unit gap inside a letter. There is no three-unit gap after the first S or after the O. That is what makes it sound like one call rather than a string of letters.

The two letters have short patterns of their own: S is ... and O is --- in the Morse code alphabet. What makes SOS distinct is the way they are joined.

Why SOS became the distress call

Before SOS, ships used a mix of company signals. The Marconi company had CQD, which other operators did not always recognize. An international radiotelegraph conference in Berlin adopted SOS in 1906, and the new signal took effect in 1908.

The pattern was chosen for practical reasons. It is long enough to stand out from routine traffic, simple enough to send with a failing transmitter, and clear to operators who did not share a language. The Titanic sent it in 1912, and press coverage fixed it in public memory.

It does not mean "save our souls"

The letters were not chosen as initials. "Save our souls" and "save our ship" were attached to the signal later. SOS is a prosign, so it has no expanded meaning; the rhythm is the point. Other prosigns, such as AR and SK, are listed on the Morse code chart.

How to send SOS

Send three short signals, three long, three short. In the Morse code translator, type SOS and press play, or type ... --- ... into the Morse column and read the decoded text. Keep every dash three times the length of a dot.

Light works the same way. Cover and uncover a lamp in that rhythm and the message carries across a bay or a dark room. Radio operators still recognize the same pattern today.

The drill on this page plays SOS against AR, SK and BT. The distress call is the longest of the four and the only one that never breaks: listen for nine marks run together.

SOS next to other calls

Mayday is the voice distress call; SOS is the Morse one. Neither is a way to ask for a tow or a spare part. Both mean immediate danger to life.

Frequently asked questions