Alarm Clock

An alarm clock (or sometimes just an alarm) is a clock designed to alert an individual or group of individuals at a specific time. The main function of this clock is to awaken people from their night's sleep or take a nap; it is sometimes used for other reminders as well. Most use sound; some use light or vibration. Some have sensors to identify when a person is in a mild sleep stage, to avoid waking up someone who is sound asleep, which causes fatigue, even if the person has adequate sleep. To turn off the sound or light, the button or handle on the clock is pressed; most clocks automatically turn off the alarm if left unattended long enough. The classic analog alarm clock has an extra hand or inset dial that is used to determine when the alarm will ring. Alarm clocks are also used in cell phones, watches and computers.

Many alarm clocks have a radio receiver that can be set to start playing at a specific time, and are known as clock radios. Some alarm clocks can set multiple alarms. The progressive alarm clock can have different alarms for different times (see next generation alarms) and play music of the user’s choice. Most modern televisions, computers, mobile phones and digital watches have an alarm function that turns on or sounds a signal at a specific time.