Morse code in Cayo Largo del Sur, Cuba is coded as "UCL", and UCL in Morse code is transmitted on its radio frequency. In some countries, during periods of maintenance, the facility may radiate a T-E-S-T code () or the code may be removed which tells pilots and navigators that the station is unreliable. In Canada, the identification is removed entirely to signify the navigation aid is not to be used. In the aviation service, Morse is typically sent at a very slow speed of about 5 words per minute. In the U.S., pilots do not actually have to know Morse to
Spelling alphabet to 1959. For the 1959–Present phonetics, the underlined syllable of each letter word should be emphasized, and each syllable of the code words for the figures (1969–Present) should be equally emphasized. After WWII, the major work in producing a better spelling alphabet was conducted by the ICAO, which was subsequently adopted in modified form by the ITU and IMO. Its development is related to these various international conventions on radio, including: The ICAO Radiotelephony Alphabet is defined by the International Civil Aviation Organization for international aircraft communications. Defined by the Association of Public-Safety Communications Officials-International. The APCO first suggested that