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
History of the Greek alphabet and "qōph" represented sounds that were not distinctive in Greek—at most, they may have been identified with allophones determined by the following vowel. The letter qoppa was used in certain Greek dialects (notably the western dialects, which ultimately gave rise to Etruscan and eventually the Latin alphabet), but elsewhere dropped out of general use. It is possible that qoppa had been assigned to the Ancient Greek , and when that sound shifted to , the letter qoppa continued as the letter phi. Phoenician had three letters, "sāmekh, ṣādē" and "šin", representing three or probably four voiceless sibilant sounds, whereas Greek