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
American Morse code a type of distortion called dispersion that gets progressively worse with the length of the cable. Dispersion severely limits the rate that Morse can be sent because of intersymbol interference. For instance, the first transatlantic telegraph cable of 1858 could only sustain a transmission rate of less than 1 word per minute. This interference is worse with American Morse because it has a greater proportion of closely spaced dots than the Gerke code. The Gerke code was adopted as a standard for transmission over cables by the Austro-German Telegraph Union (which included many central European states) at a conference in