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 alphabet added in the Arabic alphabet include these (except for , which survives as a separate phoneme in Ge'ez ሠ): One modern national alphabet that has not been graphically traced back to the Canaanite alphabet is the Maldivian script, which is unique in that, although it is clearly modeled after Arabic and perhaps other existing alphabets, it derives its letter forms from numerals. Another is the Korean Hangul, which was created independently in 1443. The Osmanya alphabet was devised for Somali in the 1920s by Osman Yusuf Kenadid, and the forms of its consonants appear to be complete innovations. Among alphabets