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
Morse code mnemonics the elements of the Morse code characters onto pictures for easy memorization. For instance, "R" () might be represented as a "racecar" seen in a profile view, with the two wheels of the racecar being the dits and the body being the dah. Syllabic mnemonics are based on the principle of associating a word "or" phrase to each Morse code letter, with stressed syllables standing for a dah and unstressed ones for a dit. There is no well-known complete set of syllabic mnemonics for English, but various mnemonics do exist for individual letters. In the Czech language, the mnemonic device