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 abbreviations the same as the prosign for "end of telegram", and the widely used but non-ITU "Over to you only" prosign is the official code for open parenthesis [(] or "left bracket". The listener is required to distinguish the meaning by context. In the example casual conversation between two station operators, above, the Morse transmissions in the grey boxes show the equal sign [=] in the same way that a simple electronic automatic Morse code reader with a one- or two-line display does: It can't distinguish context so it always displays the math symbol. It would also display an open parentheses