This might become a somewhat lengthy post, but I’ll try to keep it simple.
The USCF rulebook does not seem to speak to the standardization of digital clock settings. After having read the rules on players calling a flag down with no help from the spectators or the TD, it seems that the spirit of the rules is that a digital clock should show time elapsed and some kind of signal for flag up/down for both sides, but it should not call attention to the flag. Some settings emit a sound if one side flags while others halt both clocks and clearly show which side flagged first. I infer that these settings are not ideal since it seems the rules place the burden on the player to notice a fallen flag and the person who flags first has a glimmer of hope that if the other person flags also without noticing the first flag, no time fortfeit can be claimed. Does anyone else have opinions or citations regarding proper digital clock settings?
A second issue I’ve noticed on my Chronos Digital (black plastic buttons, no separate on/off switch), is that using a move counter has one drawback that could be major. I played in a tournament with the time control 40/2, 20/1, 30/30. While the TD was watching, my (White) opponent’s time went to zero and noticeably stopped before he hit the clock on his 40th move. He began asking the TD, “Did I make it? Did I make it?” With progressive time controls and move counters, the Chronos immediately gave him 1:00:00 hours with absolutely no deduction even though he overstepped the first time control. I was concentrating so much on making my 40th Black move in the next 30 seconds that I didn’t notice the flag, didn’t make a claim, made my 40th move, no forfeit ensued, and I went on to lose the game. The TD told me later that all I had to do was make a claim in the time before my 40th move and he would have ruled a forfeit. I didn’t really mind losing the game since I had really been outplayed, but I later tested my Chronos with move counter progressive controls and found that unless the TD is watching, claiming a win on time when the opponent hits the clock on his 40th move would have been very difficult because the Chronos does not preserve the evidence. Since that time, I’ve switched to setting DN-2 which simply counts down time with no move counter. With this setting in the above scenario, a TD who had not been present during the flag fall would be able to see that with his 40th move completed, my opponent used up 3 seconds of the second time control and should lose on time.