Alarm clock
A clock that alerts at a specified time.
An alarm clock is a clock designed to alert an individual or group at a specified time, primarily to awaken people from sleep or short naps, though it can also serve other reminders. Most alarm clocks produce sounds, light, or vibration, and some include sensors to detect light sleep stages to avoid waking a deeply sleeping person, which can cause tiredness even after adequate sleep. The alarm is typically turned off by pressing a button or handle, and many clocks automatically shut off if left unattended. A classic analog alarm clock features an extra hand or inset dial to set the alarm time.
- first_known_user
- Plato (428–348 BCE)
- first_american_alarm_clock
- Levi Hutchins, 1787
- first_patent_for_adjustable_mechanical_a
- Antoine Redier, 1847
- first_radio_alarm_clock_inventors
- James F. Reynolds and Paul L. Schroth Sr., 1940s
- field
- Timekeeping and consumer electronics
- known_for
- Awakening people at a set time, often with sound, light, or vibration
Lore & Background
The ancient Greek philosopher Plato (428–348 BCE) was said to possess a large water clock with an unspecified alarm signal similar to a water organ, used at night possibly to signal the start of his lectures at dawn. The Hellenistic engineer Ctesibius (fl. 285–222 BCE) fitted his clepsydras with dials and pointers and added alarm systems that could drop pebbles on a gong or blow trumpets at preset times. The late Roman statesman Cassiodorus (c. 485–585) advocated the water clock as a useful alarm for monastic life, and the Christian rhetorician Procopius described a complex public striking clock in Gaza before 529 that featured an hourly gong and moving figures.
Reader's Guide
The alarm clock has evolved from ancient water clocks with alarm signals to modern digital and radio devices. In China, the Buddhist monk Yi Xing (683–727) devised a striking clock, and later engineers Zhang Sixun and Su Song integrated striking mechanisms in astronomical clocks. A water-powered clock tower near the Umayyad Mosque in Damascus struck once every hour, documented in a 1203 book by Riḍwān ibn al-Sāʿātī. In 1235, a monumental water-powered alarm clock in Baghdad announced prayer hours. From the 14th century, Western European clock towers chimed at fixed times, with the St Mark's Clocktower in Venice (1493) being a famous example. User-settable mechanical alarm clocks appeared in 15th-century Europe, using a ring of holes and a pin. The first American alarm clock, made by Levi Hutchins in 1787, rang only at 4 am. Antoine Redier patented the first adjustable mechanical alarm clock in 1847. During World War II, U.S. alarm clock production ceased in spring 1942 but resumed in November 1944 due to critical shortages affecting war workers. The first radio alarm clocks were invented in the 1940s by James F. Reynolds and Paul L. Schroth Sr. Modern alarm clocks include digital, clock radio, computer, and mobile phone versions, with some offering multiple alarms, nature sounds, or sleep-stage sensors.
Did You Know?
- The ancient Greek philosopher Plato (428–348 BCE) used a water clock with an alarm signal similar to a water organ.
- The first American alarm clock, made by Levi Hutchins in 1787, only rang at 4 am and was made for his personal use.
- Alarm clock production in the United States ceased in spring 1942 due to World War II but resumed in November 1944.
- Some modern alarm clocks have sensors to detect light sleep stages to avoid waking a deeply sleeping person.
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