1) American invention 2) Clock design 
An alarm clock (or sometimes just an alarm) is a clock that is designed to make a sound, or some other signal, at a specific time. The primary utility of these clocks is to awaken people from their night`s sleep or short naps; they are sometimes used for other reminders as well. Most use sound; some use light or vibration. Some have sensors to id....
[n] - a clock that wakes sleeper at preset time
noun a clock that wakes sleeper at preset time
a clock with a bell or buzzer that can be set to sound at a particular time, as to awaken someone.
Feature you can set to go off at specified times of the day.