An alarm clock serves one purpose. It wakes us up in the morning at a designated time. The most common reason most of us use an alarm clock to wake us up is so we will not be late for work. An alarm rings until the device that shuts it off is pressed. It is activated when the time the clock was set for is reached, triggering a system that sets off the alarm.

Old-fashioned alarm clocks had a bell on the top that would ring. Today, digital alarm clocks have all kinds of noises that can be programmed. Battery powered alarms usually have a buzzing ring, and novelty alarm clocks can do all kinds of interesting wake up things. Alarm clocks can also be a part of a clock radio. At the designated set time, the radio will turn on, as well as a buzzer or beeper to wake you up. Clock radios may also offer a snooze button that you can hit to get an extra 10 to 15 minutes of sleep.

If the power goes out, some digital clock radio alarms have a battery driven back up that kicks in the event of an outage. You may own a personal laptop computer that has a built in alarm clock. If it did not come with your system, you can purchase software to install one that will give you personalized tones, online features like the news and weather reports, etc. You can program it to play your favorite song to wake up to.

The latest in alarm clocks are called next generation alarms that include sunrise alarm clocks, dawn simulators and progressively auditory clocks. These alarm clocks are designed based on the theory that there are different sleep stages at awakening and a regular alarm causes grogginess, whereas these next generation alarms ease you into awakening.