The rule book itself seems to be a bit mixed up on this issue. Here are the relevant rule examples I found:
Rule 16B. How to set clocks. “Time delay clocks should be set according to the manufacturer’s directions so that the device used to indicate a player’s time has been exhausted for all time control periods is activated. Such mechanism may include one or more of a beep, a light, a display of all zeros, or a display of a flag.”
Rule 5G. The flag. “Monitoring of each player’s time is effected by means of a clock equipped with a flag or other special device used to signal the end of a time control; the flag falls to indicate the player’s time has been used up. Some digital clocks have a beep, a light, or a display of all zeros to indicate that the player’s time has been exhausted.”
These rules seem to suggest that the beep function when time runs out on a digital clock should be turned on. And then there are rules like this:
Rule 13C1. Only players may call flag. “Only the players in a game may call attention to the fall of a flag;”
“Spectators, including players of other games, who point out the fall of a flag in any manner, may be disciplined by the tournament director to the point of expulsion from the playing room, loss of their own games, or expulsion from the tournament. The recipient of such assistance may also be penalized.”
I believe outside assistance in any game to be a serious offense, and any outside aid to bring attention to a player’s fallen flag is wrong. It is the player’s responsibilty to pay attention to the clock situation, and nothing should be allowed to alert the players. This is exactly what I feel is happening with the digital clocks set to beep when a player’s time runs out.
Why would we exclude other people from bringing attention to a fallen flag, and yet we allow another outside source (the clock) to do so? This concept does not make sense to me.
If we don’t want to allow any outside interference in a tournament chess game, then let’s not allow any outside interference, including the clock. I believe it’s as simple as that.
I announce to my players that any outside assistance in a game is illegal in a tournament, so all digital clocks are to be set with the beep at end function turned off. Any violators may be seriously penalized.
I have not yet had any problems with this issue in my tournaments.