Timer does not stop after the end of

The stopwatch function I use rarely, but the Timer regularly during training station. So I need a clear signal, and, at best, an automatic jump back to the set time after the set time. Then the participants could change stations. Then restart timer etc. This timer here are after the time a signal and is then automatically moving again. For my application completely useless.

I've been looking here for Stopwatch Timer and got shown among others this. Why is there product if it does not rewrite the functions clearly? One set would have been enough to avoid this bad buy.

The 3 star I forgive, because the device according to the instructions work. The functioning of the article, however, is not suitable for my application.