[Rostislav Persion] wrote a simple Morse Code decoder to run on his Arduino ... The other difficulty these decoders faced was detecting the signal in low signal-to-noise ratio environments ...

The use of SOS soon became universal, and the standard signal ruled the high seas until early 1999. Then, in an agreement engineered by the United Nations, Morse Code itself was officially retired ...

The signals were sent in Morse code from Poldhu, Cornwall, in England. Marconi later wrote about the experience: Shortly before midday I placed the single earphone to my ear and started listening.