Fun fact about that: in morse code, SOS is a prosign. This means it gets its own special rules.

Rather than being three seperate letters (… — …), it’s one letter without any letter spaces (…—…). This is something that applies to all prosigns in morse code, though most of them are just two letters long.

Also, when sending it on repeat you just continue the pattern without any spaces. Instead of …—… …—… (with a letter space) or …—…/…—… (with a word space), you send …—…—…—…—… and just keep continuing the pattern. iirc SOS is the only prosign where this is a thing.

Other prosigns are for example HH (…) to indicate a correction to something previously sent, and SK (…-.-) (silent key) to signal that you have finished with the current conversation and the frequency is now clear.