SOS doesn't stand for "Save Our Souls." It doesn't stand for "Save Our Ship," either. It doesn't stand for anything. The rules that created it describe only a rhythm: three dots, three dashes, three dots, ... --- ..., sent as one unbroken signal.
Before SOS
Wireless telegraphy arrived on ships around 1900, and at first there was no agreed way to call for help by radio. Several signals competed:
- CQD: from 1 February 1904, the Marconi company told its operators to use CQD: the general call "CQ" with a "D" added for distress. ("Come Quick, Danger" is a later backronym.)
- SSS DDD: suggested at the 1903 Berlin preliminary conference by the Italian delegate, Captain Quintino Bonomo. Procedures were outside that conference's scope, so nothing was adopted.
- NC: the International Code of Signals flag signal for "in distress; want immediate assistance", which the US Navy proposed in 1906 for radio use.
Where SOS came from
Germany got there first. Radio regulations that took effect on 1 April 1905 defined three Morse sequences, including a distress signal (Notzeichen) of three dots, three dashes and three dots. Another, the calling signal (Suchzeichen), was three dots, three dashes and a single dot (... --- ., which reads as SOE). SOE was a call, not a distress signal.
The first International Radiotelegraph Convention, signed in Berlin on 3 November 1906, adopted the German distress signal for everyone. Its service regulations said simply that ships in distress shall use that signal, repeated at brief intervals. The convention took effect on 1 July 1908.
Why that pattern?
The regulations don't say. Neither the German rules nor the 1906 text gives a reason for the choice, and you'll find confident explanations online that cite nothing. What can be said is what the pattern is like to use:
- It is only nine elements long, and it is easy to send and to recognise, even for someone who knows no other Morse.
- Sent unbroken, it is one continuous shape rather than three letters.
- Written as letters, "SOS" reads the same upside down, which helps when it is marked on the ground to be seen from the air.
The letters came afterwards. Because three dots is S and three dashes is O in International Morse, people soon started calling the signal "SOS"; Electrical World was already doing so in January 1907.
First uses
The earliest ships reported to have sent SOS are the Cunard liner RMS Slavonia, wrecked in the Azores on 10 June 1909, and the steamer SS Arapahoe, off North Carolina on 11 August 1909. Some Marconi operators were slow to switch: in April 1912 the operators on the RMS Titanic sent both CQD and SOS.
The retroactive meanings
"Save Our Souls" and "Save Our Ship" are backronyms: meanings invented after the fact to make the letters memorable. They're harmless, but they're not why the signal exists.
The end of SOS as the maritime radio standard
The Global Maritime Distress and Safety System (GMDSS) replaced Morse for ocean distress. Ships had to carry the full GMDSS equipment by 1 February 1999, and now raise the alarm with satellite beacons (EPIRBs) and digital selective calling. The Maritime Radio Historical Society dates the last commercial Morse transmission in the US to 12 July 1999, and marks the date each year with its "Night of Nights" broadcast.
SOS today
SOS is still an official distress signal. US navigation rules list "a signal made by any method" consisting of the SOS group among the signals that indicate distress and need of assistance (33 CFR 87.01(d), the US text of Annex IV of the collision regulations). In practice that means:
- A flashlight: three short, three long, three short flashes. Phones don't do this by themselves; the iPhone flashlight, for one, only turns on and off and changes brightness.
- A whistle: same rhythm.
- Knocking on metal, pipes or walls.
- Letters on the ground, big enough to be seen from the air.
Try it now: open the translator with SOS pre-filled, hit Play, and listen to the rhythm. Press Flash and your screen flashes it.
Frequently asked questions
Does SOS actually stand for anything?
No. The 1905 German rules and the 1906 international regulations define it only as a Morse rhythm, ... --- .... "Save Our Souls" and "Save Our Ship" are backronyms invented afterwards.
What is the SOS pattern in Morse code?
Three dots, three dashes, three dots, ... --- ..., sent as one continuous signal with no gaps between the letters, so the ear hears a single repeating shape.
How do I signal SOS with a flashlight?
Three short flashes, three long flashes, three short flashes, then pause and repeat. Our emergency cheat sheet covers light, sound, and tapping methods.
Is SOS still an official distress signal?
Yes. It stopped being the maritime radio standard in 1999, when GMDSS took over, but SOS sent by any method is still listed as a distress signal in the collision regulations (in the US, 33 CFR 87.01(d)).