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
American Morse code a type of distortion called dispersion that gets progressively worse with the length of the cable. Dispersion severely limits the rate that Morse can be sent because of intersymbol interference. For instance, the first transatlantic telegraph cable of 1858 could only sustain a transmission rate of less than 1 word per minute. This interference is worse with American Morse because it has a greater proportion of closely spaced dots than the Gerke code. The Gerke code was adopted as a standard for transmission over cables by the Austro-German Telegraph Union (which included many central European states) at a conference in