Morse code and interword gaps may be lengthened so the word rate is only 5 words per minute. Using different character and text speeds is, in fact, a common practice, and is used in the Farnsworth method of learning Morse code. Some methods of teaching Morse code use a dichotomic search table. Morse Code cannot be treated as a classical radioteletype (RTTY) signal when it comes to calculating a link margin or a link budget for the simple reason of it possessing variable length dots and dashes as well as variant timing between letters and words. For the purposes of Information Theory
Morse code 1945. Morse code was used as an international standard for maritime distress until 1999 when it was replaced by the Global Maritime Distress Safety System. When the French Navy ceased using Morse code on January 31, 1997, the final message transmitted was "Calling all. This is our last cry before our eternal silence." In the United States the final commercial Morse code transmission was on July 12, 1999, signing off with Samuel Morse's original 1844 message, "What hath God wrought", and the prosign "SK". As of 2015, the United States Air Force still trains ten people a year in Morse.