causes tiredness, even if the person has had adequate sleep. To turn off the sound or light, a button or handle on the clock is pressed; most clocks automatically turn off the alarm if left unattended long enough. A classic analog alarm clock has an extra hand or inset dial that is used to show the time at which the alarm will ring.

Many alarm clocks have radio receivers that can be set to start playing at specified times, and are known as clock radios. Additionally, some alarm clocks can set multiple