Someone was recently asking why MFS and many other fire services around the world use the letter K in there radio transmissions, this might explain it - sort of.
WHAT DOES THE LETTER K MEAN?
The use of the letter K is a holdover from the days of telegraph. It was sent at the end of a transmission to indicate that I am finished sending and I await your reply. It is similar to the military use of the word over.
Hmm, still doesnt fit well with the MFS K(number). Certainly applies when you hear the yanks say (Message), K. though