Alarm clock
type of clock used to wake up a sleeping person at a certain time
An alarm clock or alarm is a clock that is designed to alert an individual or group of people at a specified time. The primary function of these clocks is to awaken people from their night's sleep or short naps; they can sometimes be used for other reminders as well. Most alarm clocks make sounds; some make light or vibration. Some have sensors to identify when a person is in a light stage of sleep, to avoid waking someone who is deeply asleep, which 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 alarms. A 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 alarm functions that automatically turn on or sound alerts at a specific time.
Begin with the source’s own compact description: “Alarm clock” is type of clock used to wake up a sleeping person at a certain time. The dossier treats that line as a proposition to test through Alarm, clock and type, not as a finished interpretation.
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Named sources, stable identifiers and responsible institutions provide the strongest route from overview to verifiable evidence. The source revision retrieved here is dated Aug 15, 2026. The linked authority identifier is Q212758. The Library of Congress control number is sh2004007158. None of the 1 selected statements returned an explicit reference.
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This entry incorporates text from “Alarm clock” on English Wikipedia. Contributors are listed in the page history. Text is available under the Creative Commons Attribution-ShareAlike 4.0 License. Selected authority identifiers and statements are retrieved from Wikidata under CC0; their references and qualifiers remain part of the verification path.