On the other hand, the letter O in the older American Morse was relatively short because it contained an "long" internal gap: "dit-dit" (as opposed to I being "

On the other hand, the letter O in the older American Morse was relatively short because it contained an "long" internal gap: "dit-dit" (as opposed to I being "didit" and the "word" EE being "dit, dit"). If the regular gap is the length of a dot, and the inter letter gap is the length of three dots, the length of the gap in O was two dots. International Morse eliminated the "long" internal gap (according to Wikipedia [1], this had an advantage on the first long undersea cables), so O had to be re-encoded. '---' ("dahdahdah") was the only three-element code not already being used for a letter. (It happens to be the number 5 in American Morse.) When I was a Novice-class ham many years ago, I found that older hams would sometimes send the pro sign C (in the sense of "confirm" or "yes") as didit-dit instead of dahdidahdit. I never really understood why; I just went along with it. Turns out didit-dit is C in American Morse. [1] https://en.wikipedia.org/wiki/American_Morse_code https://en.wikipedia.org/wiki/American_Morse_code