Morse code most common letter in English, the letter "E", has the shortest code: a single dot. Because the Morse code elements are specified by proportion rather than specific time durations, the code is usually transmitted at the highest rate that the receiver is capable of decoding. The Morse code transmission rate ("speed") is specified in "groups per minute", commonly referred to as "words per minute". Morse code is usually transmitted by on-off keying of an information carrying medium such as electric current, radio waves, visible light or sound waves. The current or wave is present during time period of the dot
History of the International Phonetic Alphabet closely connected that the whole might be treated as a single sound", were noted as able to be represented with a tie bar, as in . Palatalized consonants could be marked by a dot above the letter, as in , "suggesting the connexion with the sounds i and j". The 1921 "Écriture phonétique internationale" introduced new symbols, some of which were never to be seen in any other booklet: The book also mentioned symbols "already commonly used in special works", some of which "have not yet been definitively adopted": It also introduced several new suprasegmental specifications: It recommended the use