The sound you can hear by clicking on the control above is a recreation of part of one of the Titanic's distress calls sent by Marconi operator Jack Phillips (left) aboard RMS Titanic just after midnight on Monday, April 15, 1912.
As best as my rudimentary Morse code skills allow, the message translates as follows:
CQD CQD SOS SOS CQD DE MGY MGY MGY
"CQD" was the standard distress call at the time; there were a whole series of "CQ" codes, and the "D" meant distress. In 1909, an international convention adopted "SOS" as the new distress signal-- not because it means "save our souls," as is often reported, but because the three dots, three dashes and three dots are a very distinctive signal that cannot be confused with anything else, especially by those not very familiar with Morse. (Even you can hear it, right?) "MGY" were Titanic's call letters. And the "DE" means "from."
Imagine sitting in some radio shack on one of the many ships in the North Atlantic that cold, still night, listening to the staccato mutter of the Morse spark, and suddenly hearing this call out of the ether. Anyone who heard the call that night remembered to his dying day the hair rising on the back of his neck at the almost incomprehensible message -- the Titanic in distress.