Morse code become commonly available until around 1920. Until 2003, the International Telecommunication Union mandated Morse code proficiency as part of the amateur radio licensing procedure worldwide. However, the World Radiocommunication Conference of 2003 made the Morse code requirement for amateur radio licensing optional. Many countries subsequently removed the Morse requirement from their licence requirements. Until 1991, a demonstration of the ability to send and receive Morse code at a minimum of five words per minute (wpm) was required to receive an amateur radio license for use in the United States from the Federal Communications Commission. Demonstration of this ability was still
Morse code abbreviations only. To station S1 from station S2. Roger (R) Thank you (TU) see you again (CUAGN) Best regards (73) To station S1 from station S2: Signing off. In International Morse code there is no "distinct" dot-dash sequence defined only for the mathematical equal sign [=]; rather the same code ("–···–" or "dah di di di dah") is shared by "double hyphen" [=] and the procedural sign for "section separator" notated as . It is fairly common in the "Recommended International Morse Code" for punctuation codes to be shared with prosigns. For example, the code for plus or cross [+] is