The bellringer question confuses me. I tried Googling for the answer and found a couple of sites where people have discussed at length the calculation required to work out the answer. The answer that seemed to occur most often was 11 seconds.
My brain is too tired to even think about it but will try it again later if none of our resident geniuses can agree on an answer. :-)
This is a standard puzzle: since there are 3 gaps between 4 rings and that takes 3 seconds, then each gap is 1 second. Thus for 12 rings there are 11 gaps which takes 11 seconds.
For four rings there are only 3 time intervals between them. If that take 3 seconds then each interval is one second long. For twelve rings there are 11 time intervals so it takes eleven seconds.
Thanks to all of you. My initial answer was 12 seconds but that was much too simple and I decided that it was wrong (which it was) but then my brain seized up.
Should I win the euromillions draw jackpot tonight I will send each of you a small reward. :-)