Ship's bells
At sea the day is cut into four-hour watches, and the bell counts the half hours. One bell after the first half hour, two after the second, up to eight bells, and then the watch ends and the count starts again.
The rings come in pairs, so a tired sailor can count them in twos rather than one at a time. Eight bells means your watch is over, which is why the phrase came to mean the end of something altogether.
Nobody needs to see anything, and nobody needs to speak. A number, carried by sound, through fog and through sleep.
Drums that talk
Talking drums do something cleverer than counting. In tonal languages the pitch of a word is part of its meaning, so a drum that can slide between a high note and a low one can copy the shape of speech itself. It is not spelling, and it is not a codebook. It is the tune of the sentence with the words taken out.
Because a lot of information is lost that way, drummers add stock phrases to make each message longer and clearer, which is exactly what the NATO alphabet does with Alfa and Bravo: use more, so that less can go wrong.
Whistled languages do the same across valleys. Both carry for miles, which is the point, and both can be heard by everyone in range, which is the problem.
And smoke
Smoke signals are the oldest of these and the most misunderstood. Little of it is an alphabet. Mostly it is a codebook of a handful of agreed meanings: come back, danger, all is well, gather here. The number of puffs and where the fire is lit are the message.
One column of smoke on a hilltop can be seen for twenty miles, and it says one thing very loudly to everyone who can see it. That is the whole trade-off in this branch: enormous reach, no privacy at all.
Back to signals The ciphers