timer

A timer is a type of clock used for measuring specific times.
Timers can be categorized into two main types.
The word "timer" is usually reserved for devices that count down from a specified time interval called a countdown timer, while devices that do the opposite, measuring elapsed time by counting upwards from zero, are called stopwatches. A simple example of the first type is an hourglass. Working method timers have two main groups: hardware and software timers.
Most timers give an indication that the time interval that had been set has expired - such as a loud noise.
Time switches, timing mechanisms that activate a switch, are sometimes also called "timers."

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