timer

A timer or countdown timer is a type of clock that starts from a specified time duration and stops when reaching 00:00. A simple timer is an hourglass. Commonly, a timer triggers an alarm when it ends. A timer can be implemented through hardware or software.
Stopwatches operate in the opposite direction, upwards from 00:00, measuring elapsed time since a given time instant.
Time switches are timers that control an electric switch.

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