The Letter S - Marconi's First Transatlantic Signal, 1901 The message that opened the radio century was three dots. On 12 December 1901, Marconi claimed to hear the letter S in Newfoundland, sent from Cornwall - and the Atlantic has been getting smaller ever since. Why three dots The test signal had to survive scepticism as much as static. A single dot could be a crackle; three evenly spaced dots could not be an accident. The choice was scientific as much as practical. From stunt to system Critics demanded proof; within a year, verified two-way exchanges followed, then commercial service. The three dots of 1901 became the direct ancestor of the three-by-three pattern the world would adopt as SOS. Translate any text to Morse code, play it as sound and download the audio free at: https://morsecodeworks.com/