MGY was the callsign of the ship and the code for emergency was CQD but for the first time in history they transmit also SOS - Save Our Souls the signal who became a mark since then.
To mark 100 years since the Titanic incident a lot of radio amateurs special callsigns will operate all over the world in all bands and modes.
the Radio room
SDR - DDH47
Despite all versions and theories, i think the real reason for Titanic sinking is "defiance". Remember the spirit of that time and the "pride" without limits; on that not even God can sink it!
S.O.S. S.O.S. S.O.S. S.O.S. S.O.S. S.O.S. S.O.S.