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 procedure word "ALL AFTER", and is used to indicate that part of the previously transmitted message needs to be re-transmitted; the only difference between the Morse code prosigns is an inter-letter space between the two "dot dash dot dash" sequences". Because there are no letter boundaries in the transmitted prosigns, their division into letters is arbitrary and may be done in multiple equivalent ways. For example, ' (+) is exactly equivalent to ' (+) and ' (+). Likewise, the well-known prosign ' could just as well be written ' (++), ' (++), or even (+). Normally, one particular form is