Facts about alarm clocks

• An alarm clock is a clock that is designed to make a loud sound at a specific time. Traditional mechanical alarm clocks have one or two bells that ring, but digital alarm clocks can make other noises.
• The first radio alarm clock was invented by James F. Reynolds, in the 1940s and another design was also invented by Paul L Schroth Sr.
• The deaf and hard of hearing are often unable to perceive auditory alarms when asleep. They may use specialized alarms, including alarms with flashing lights instead of or in addition to noise.
• Among annoyances caused by alarm clocks is sleep inertia, a feeling of grogginess that results from abrupt awakening. Progressive alarm clocks claim to solve this issue. They include sunrise alarm clocks, dawn simulators and progressive auditory alarm clocks.
• Simple battery-powered alarm clocks make a loud buzzing sound, or other similar noise to wake a sleeper, while novelty alarm clocks can speak, laugh, or sing.
• 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 signalling the beginning of his lectures at dawn (Athenaeus 4.174c).
• 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.
• In China, a striking clock was devised by the Buddhist monk and inventor Yi Xing (683–727).
• 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.