It was introduced by the German government in radio regulations on April 1 , 1905 . It became the worldwide standard when it was included in the second International Radiotelegraphic Convention , which was signed on November 3 , 1906 . This distress signal was first adopted by the German government in radio regulations effective April 1 , 1905 , and became the worldwide standard under the second International Radiotelegraphic Convention , which was signed on November 3 , 1906 and became effective on July 1 , 1908 .