What do timekeepers do?

Timekeepers keep the time of a speech in a debate.

eg. My debate speech's maximum amount of time in 3 minuets and 30 seconds.

the timekeeper will keep the time and when it gets to 3 minuets your timekeeper will ring a warning bell at 3 minuets and the bell to stop at 3 minuets and 30 seconds.

the time and warning bell will vary