Alarm clock

An alarm clock or alarm is a clock that alert an people or group of people at selected time such as 7:00AM. Most alarm clocks can make the sound to wake people up; some alarm clocks can make light or vibration. They can turn off sound or light just press button or handle. A classic along alarm clock has an extra hand or inset dial that how alarm will ring at selected time.

Most newer television, computers, mobile phones and digital watches have alarm features that automatically turn on or sound alerts at a selected time.

 Mobile phones alarms 
Many newer mobile phones have built-in alarm clock that do not need the phone to be turned on for the alarm to ring off. iPhone 2G became the first iPhone model to has a alarm function. Some of these mobile phones can set the alarm ringtone. Music can be downloaded to the phone and then chosen to play for waking.

 References 

Category:American inventions
Category:Sleep