A clock that wakes you at a set time using sound or vibration; commonly called an alarm clock or alarm.
毎朝、目覚まし時計で七時に起きる。
I wake up at seven every morning with an alarm clock.
目覚まし時計が鳴らなかったので寝坊してしまった。
The alarm clock didn't go off, so I overslept.
最近はスマホのアラームを目覚まし時計代わりに使う人が多い。
Nowadays many people use their smartphones' alarm as an alarm clock.