timer

She set a timer for certain math problems — so all students knew they were being challenged to pay attention and move quickly.

He also recalled an incident where the "beep" of a timer was used to signal that one attack was to stop and another to start.

Or using a timer with limits on how long each person’s shower should be.

Set a timer for 10, 15 or 20 minutes and commit to working on one item on your to-do list until the alarm goes off.

It said it was "not persuaded" that it called into question the judges' conclusion that the fragment came from an MST-13 timer which triggered the bomb.