Alarm clock

clock radioalarmalarm clocksNext-Generation Alarmssetting alarmssnooze buttonWecker
An alarm clock (alarm for short) is a clock that is designed to alert an individual or group of individuals at specified time.wikipedia
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Watch

wristwatchwatchesdigital watch
Alarm clocks are also found on mobile phones, watches, and computers.
Most electronic quartz watches, on the other hand, include time-related features such as timers, chronographs and alarm functions.

Radio receiver

receiverreceiversRadios
Many alarm clocks have radio receivers that can be set to start playing at specified times, and are known as clock radios.
Clock radio - A bedside table radio that also includes an alarm clock. The alarm clock can be set to turn on the radio in the morning instead of an alarm, to wake the owner.

Mainspring

springspring motorspring-wound
Traditional mechanical alarm clocks have one or two bells that ring by means of a mainspring that powers a gear to propel a hammer back and forth between the two bells or between the interior sides of a single bell.
This type is often used on alarm clocks, music boxes and kitchen timers where it doesn't matter if the mechanism stops while winding.

Clock

clockstimepiecemechanical clock
An alarm clock (alarm for short) is a clock that is designed to alert an individual or group of individuals at specified time. A classic analog alarm clock has an extra hand or inset dial that is used to specify the time at which to activate the alarm.

Digital clock

digitalcomputer programmingDigital clocks
Digital alarm clocks can make other noises.
This is a particular problem with alarm clocks that have no "battery" backup, because even a very brief power outage during the night usually results in the clock failing to trigger the alarm in the morning.

Levi Hutchins

The first American alarm clock was created by Levi Hutchins, of New Hampshire in the United States, in 1787.
Levi Hutchins (August 17, 1761 - June 13, 1855) was an American clockmaker, and inventor of the first American alarm clock.

Mustansiriya Madrasah

Madrasa MustansiriyaMustansiriyaMustansiriyyah Library
In 1235, an early monumental water-powered alarm clock that "announced the appointed hours of prayer and the time both by day and by night" was completed in the entrance hall of the Mustansiriya Madrasah in Baghdad.
In 1235, an early monumental water-powered alarm clock that announced the appointed hours of prayer and the time both by day and by night was completed in the entrance hall of the Mustansiriya Madrasah in Baghdad.

Striking clock

strikingchiming clockrack and snail
30.4 f.). The Christian rhetorician Procopius described in detail prior to 529 a complex public striking clock in his home town Gaza which featured an hourly gong and figures moving mechanically day and night.
Alarm clock

Sleep

sleepingsleep architectureasleep
Scientific studies on sleep having shown that sleep stage at awakening is an important factor in amplifying sleep inertia.
Today, many humans wake up with an alarm clock; however, people can also reliably wake themselves up at a specific time with no need for an alarm.

Timer

timerstiming devicesoftware timer
Timer
They function similarly to a mechanical alarm clock; the energy in the mainspring causes a balance wheel to rotate back and forth.

Delayed sleep phase disorder

delayed sleep phase syndromea delayDelayed sleep-wake phase disorder
Delayed sleep phase syndrome
They often have asked family members to help wake them in the morning, or they have used multiple alarm clocks.

Accelerometer

accelerometersG-sensoracceleration sensor
The alarm clocks use sensing technologies such as EEG electrodes and accelerometers to wake people from sleep.
Sleep phase alarm clocks use accelerometric sensors to detect movement of a sleeper, so that it can wake the person when he/she is not in REM phase, in order to awaken the person more easily.

Clock face

dialfacehour hand
A classic analog alarm clock has an extra hand or inset dial that is used to specify the time at which to activate the alarm.

Mobile phone

cell phonemobilemobile phones
Alarm clocks are also found on mobile phones, watches, and computers.

Electromagnetism

electromagneticelectromagnetic forceelectromagnetics
In an electric bell-style alarm clock, the bell is rung by an electromagnetic circuit and armature that turns the circuit on and off repeatedly.

Electronic circuit

circuitcircuitrycircuits
In an electric bell-style alarm clock, the bell is rung by an electromagnetic circuit and armature that turns the circuit on and off repeatedly.

Armature (electrical)

armaturearmaturesarmature winding
In an electric bell-style alarm clock, the bell is rung by an electromagnetic circuit and armature that turns the circuit on and off repeatedly.

Electric battery

batterybatteriesbattery-powered
Simple battery-powered alarm clocks make a loud buzzing or beeping sound to wake a sleeper, while novelty alarm clocks can speak, laugh, sing, or play sounds from nature.

Ancient Greece

Greekancient Greekancient Greeks
The ancient Greek philosopher Plato (428–348 BC) was said to possess a large water clock with an unspecified alarm signal similar to the sound of a water organ; he used it at night, possibly for signaling the beginning of his lectures at dawn (Athenaeus 4.174c).

Plato

dialoguesPlato's dialoguesPlatonic dialogue
The ancient Greek philosopher Plato (428–348 BC) was said to possess a large water clock with an unspecified alarm signal similar to the sound of a water organ; he used it at night, possibly for signaling the beginning of his lectures at dawn (Athenaeus 4.174c).

Water clock

clepsydrawater clockswater-clock
The ancient Greek philosopher Plato (428–348 BC) was said to possess a large water clock with an unspecified alarm signal similar to the sound of a water organ; he used it at night, possibly for signaling the beginning of his lectures at dawn (Athenaeus 4.174c).

Water organ

hydraulishydraulic organearly
The ancient Greek philosopher Plato (428–348 BC) was said to possess a large water clock with an unspecified alarm signal similar to the sound of a water organ; he used it at night, possibly for signaling the beginning of his lectures at dawn (Athenaeus 4.174c).

Athenaeus

Athenaeus of NaucratisAthen.
The ancient Greek philosopher Plato (428–348 BC) was said to possess a large water clock with an unspecified alarm signal similar to the sound of a water organ; he used it at night, possibly for signaling the beginning of his lectures at dawn (Athenaeus 4.174c).

Hellenistic period

HellenisticHellenicHellenism
The Hellenistic engineer and inventor Ctesibius (fl. 285–222 BC) fitted his clepsydras with dial and pointer for indicating the time, and added elaborate "alarm systems, which could be made to drop pebbles on a gong, or blow trumpets (by forcing bell-jars down into water and taking the compressed air through a beating reed) at pre-set times" (Vitruv 11.11).