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
Prosigns for Morse code Combined Communications Electronics Board telecommunications specifications. Prosigns for Morse code Procedure signs or prosigns are shorthand signals used in radio telegraphy procedures, for the purpose of simplifying and standardizing communications related to radio operating issues among two or more radio operators. They are distinct from general Morse code abbreviations, which consist mainly of brevity codes that convey messages to other parties with greater speed and accuracy. There are also specialized variations used in radio nets to manage transmission and formatting of messages. In this usage, Morse prosigns play a role similar to the role played by the nonprinting control characters