Morse Code Telegraphy History
A ham radio friend shared this information with me via email. While reading, I found the original source of several morse code shortcuts that are commonly used by ham radio operators. Hams call these shortcuts “prosigns”.
The information seems to have originated from the winfldigi group.io forum. Those are the people who should be credited with providing and sharing the knowledge reproduced below.
First, let’s look at the history of the prosign “AA” (di-dah-di-dah). Those above a certain age may recall when it was common practice to place a comma after each line of an address, or so it was taught in many one-room school houses. This practice, of course, long ago fell by the wayside.
When the nascent telegraph industry began developing standards for transmitting telegrams, they imported this then standard practice. It had the added benefit of acting as a prosign indicating where the address or signature line ended. Because the telegraph industry in North America used the original American Morse Code, the American Morse Code comma was used for this purpose (di-dah-di-dah).
When wireless telegraphy first emerged, American Morse was commonly used for radio communications. As a matter of fact, for the first decade of the 20th century, American Morse Code was the standard on the Great Lakes and for many coastal steamship companies. The reasons are obvious; there were plenty of well trained telegraph operators around. all of whom were proficient in the American Morse Code. Of course, eventually, the Continental Code (International Morse) was adopted as standard for maritime communications due to it’s international nature, issues of safety of life at sea, and so on. However, many of the earlier telegraph procedures were imported into commercial wireless telegraphy and Amateur Radio. Here are some prosign examples:
AR (di-dah-di-dah-dit) is actually “FN” in American Morse Code representing “FINISHED.” This was sent at the end of a telegram, and it continues to be used at the end of ham radio transmissions, which are essentially telegrams themselves which are just part of a conversation or group of message exchanges.
SK (di-di-di-dah-di-dah) is actually “30” in American Morse Code. In the Western Union wire codes, “30” represented “close of work.” It was commonly sent at the end of press stories, at the conclusion of transmitting a file of telegrams, or similar practices. Hams today use it to indicate the conclusion of a QSO in much the same way.
ES (dit di-di-dit) is actually the ampersand (&) in American Morse Code. Like many American Morse characters, it has an internal space, which is slightly shorter in timing than that used between individual characters. In this respect, it shares this characteristic with other Morse characters having internal spaces, such as C, R, Y, Z and O.
One still occasionally hears hams use the Morse letter “C” (di-di dit) to ask if a frequency is in use or to indicate it’s in use.
…..and so on.
So, when radio amateurs began handling message traffic, they simply imported the techniques of commercial operators and adopted the “AA” prosign, or American Morse comma to indicate the end of a line in an address.