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
Morse code abbreviations the same as the prosign for "end of telegram", and the widely used but non-ITU "Over to you only" prosign is the official code for open parenthesis [(] or "left bracket". The listener is required to distinguish the meaning by context. In the example casual conversation between two station operators, above, the Morse transmissions in the grey boxes show the equal sign [=] in the same way that a simple electronic automatic Morse code reader with a one- or two-line display does: It can't distinguish context so it always displays the math symbol. It would also display an open parentheses