What is dot dash in morse code?

The shortest two-mark letter

A is one dit and one dah, in that order, separated by a one-unit gap. Counted out it runs to five units, which makes it the shortest character in ITU-R M.1677-1 that uses both kinds of mark. At 20 words per minute (WPM) that is 300 milliseconds from the start of the dit to the end of the dah.

It is also the pair the Morse Universe logo is drawn from: a filled circle one unit across, then a rounded bar three units long, at the proportions the standard sets.

Letters that are each other backwards

Read A backwards and you get a different letter, N. That happens all over the table, and noticing it saves learning two patterns where one will do:

• A and N: dit dah, and dah dit
• U and D: two dits and a dah, and a dah and two dits
• V and B: three dits and a dah, and a dah and three dits
• W and G: a dit and two dahs, and two dahs and a dit
• F and L: it works for four-mark letters too

A few letters read the same in both directions and so have no partner. R and K are the clearest examples, along with the single marks E and T and the doubled ones I and M.

Why the gap between the marks matters

The dit and the dah in A are one unit apart. That gap is as much a part of the character as the marks themselves, because a three-unit gap would end the letter instead: a dit, then three units of silence, then a dah, reads as E followed by T.

The three gap lengths in morse are one unit inside a character, three units between characters and seven between words. Get them wrong and the marks regroup into different letters, which is the usual reason a decoded message comes out as nonsense. There is more on that in does morse code have spaces.

Seeing the whole table

The printable morse code chart lays out all 26 letters, the ten digits and the punctuation marks at these proportions, on sheets sized for US Letter and A4. To turn a line of marks back into words, paste it into the morse code translator.