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 mnemonics the elements of the Morse code characters onto pictures for easy memorization. For instance, "R" () might be represented as a "racecar" seen in a profile view, with the two wheels of the racecar being the dits and the body being the dah. Syllabic mnemonics are based on the principle of associating a word "or" phrase to each Morse code letter, with stressed syllables standing for a dah and unstressed ones for a dit. There is no well-known complete set of syllabic mnemonics for English, but various mnemonics do exist for individual letters. In the Czech language, the mnemonic device