Ringing the bell is grounds for expulsion from many chat rooms, at least the semi-anonymous chat rooms provided by Bloomberg and other sell sides shops. Apparently it is very annoying to certain people.
If the price moves against you since you last quoted, you typically say something like "off" and ring the bell so that the other guy knows that price is not good anymore. Fairly relevant when you're talking to a salesguy who is not looking at the chat, cause he's talking with his trader