A friend and I have been having a discussion. The Colregs say that if you're under 20 meters (12 meters inland rules) you don't have to have a bell. You are still required to carry some sort of efficient sound device and you are required to make some kind of sound. From Rule
35, "However, if she does not, she shall make some other efficient sound signal at intervals of not more than 2 minutes."
He thinks short, long, short is the sound to make This is described in Rule
35. While logically this makes sense to me, I don't think this is what they intended. This sequence, the rule says, can be used in addition
to the bell signal. I believe that they would have put that sequence in the rule concerning no bells rather than saying make some other sound. I haven't found any discussion on what "other" means. Perhaps they were thinking about any sort of percussive sound, but BoatUS claims a whistle is suitable, but then we're back to what kind of a sequence would be appropriate. On another hand, a short, long, short is also "some other sound" as well.
Lucky me, I don't have to worry about it, as this same person bought me a bell as a boat warming present years ago.
Rule 35, g/f
A vessel at anchor
may in addition sound three blasts in succession, namely one short, one long and one short blast, to give warning of her position and of the possibility of collision
to an approaching vessel.