My dog has a anti-barking collar that will beep on one bark, then do a small zap on subsequent barks. After 30 seconds, it resets. She quickly learned (half border collie) that she can bark once with no ill effects. She then learned that after a while she can bark again. It is uncanny how she often gets close to 30 seconds, and almost never goes under. The times I have timed it she's been 35-45 seconds, which is a lot more precise than I would have expected. She seems to be more accurate when she paces during the interval, so I've always wondered if she's "counting" her steps.