Morse code is a system that transmits text as unique sounds or lights. It was developed in the 1800s by Samuel Morse to be used with the telegraph. Each letter A–Z and digit 0–9 has its own unique dot-dash code, where dots are short signals (or pulses of light) and dashes are long signals. In the case of the letter A, the symbol is made up of a single dot followed by a single dash: · −.
This pattern is called "di-dah" and consists of one dot (a short signal) followed by one dash (a longer signal). The timing of the letter A in Morse code follows the same pattern as any other letter; the dot comes first, followed by the dash.
Why the pattern is short
A contains two signal elements, while E contains one dot and T contains one dash. A short pattern is convenient for practice, but code length alone does not tell you how often a character occurs in a particular message. International Morse assigns each supported character a defined pattern rather than encoding its frequency directly.
How A appears in radio prosigns
The end-of-message prosign <AR> joins A (.-) and R (.-.) without a letter gap, producing .-.-.: five signal elements, not three. Enter <AR> in this site's translator to check the continuous pattern; entering plain AR instead preserves the normal gap between two letters. Prosigns communicate an operating instruction rather than an ordinary word.
The letter A also appears at the beginning of other prosigns. AS is sent as the letters A and S run together without the normal letter gap (.-...) and means wait. AA is likewise sent without an internal letter gap (.-.-) and is used for a new line. Because prosigns are continuous patterns, they should not be explained as merely changing the length of one dot.
Check the timing
At 20 WPM under standard PARIS timing, one dot unit is 60 milliseconds. A consists of a 60 ms dot, a 60 ms internal gap and a 180 ms dash: 300 ms before the following character gap. Use the timing dataset and translator to compare the letter with a continuous prosign. The reference is ITU-R M.1677-1, International Morse code.