Morse code
The people doing the communication were employees of either Marconi or Telefunken; they were not employed by the ships' owners. These operators were not allowed to answer calls sent by the competing company, which also included distress signals. As this was against the laws of the sea, a conference in Berlin decided to use the German distress signal internationally. This started in 1908. When the ship Republic sent a distress signal in 1909, it was still CQD, and the Titanic also sent CQD at first, in 1912.