On January 20 , 1914 , the London International Convention on Safety of Life at Sea adopted the Morse code signal TTT ( - - - ) , three letter Ts ( - ) spaced correctly as three letters so as not to be confused with the letter O ( - - - ) , as the `` Safety Signal , '' used for messages to ships `` involving safety of navigation and being of an urgent character . ''
On January 20 , 1914 , the London International Convention on Safety of Life at Sea adopted the Morse code signal TTT ( - - - ) , three letter T 's ( - ) spaced correctly as three letters so as not to be confused with the letter O ( - - - ) , as the `` Safety Signal , '' used for messages to ships `` involving safety of navigation and being of an urgent character . ''