How Do Alarm Clocks Work?

Unless you're unemployed and have the luxury of sleeping as late as you want each and every day, chances are you have employed an alarm clock at some point. While digital alarm clocks are much more common these days than their analog forefathers, the analog clocks still have a place in the market, and are still used by those who fear power outages or unreliability in their digital clock. Few people will admit to much fondness for their alarm clock, being the interrupter of peaceful sleep that it is, but you may have wondered how exactly it all comes together to make sure you get to work or school on time every morning when you'd rather be catching another forty winks.

This is the granddaddy of alarm clocks. Analog alarm clocks date clear back to the 1500s, although they were not patented and put into widespread use until the late 19th century. Most analog alarm clocks feature a couple of metal bells atop the fixture, and a small hammer between them, which strikes the bells to produce the sound which wakens the sleeper. Because of the acoustic properties of the alarm, most analog alarm clocks are louder than their digital counterparts, making them ideal for the deep sleeper.

Inside the analog alarm clock are a series of gears, powered by battery or wall electricity. These gears move the hands of the clock about, using an oscillating wheel to keep the time consistent. On the alarm clock will be an extra hand, typically shorter than the hour hand of the clock. This hand can be wound through a knob on the back, until the desired wakeup time is achieved. At that point, the user will flip a switch in the back to "set" the alarm. What this does is set a spring which presses against the mechanism of the bell hammer. When the hour hand reaches the point at which the alarm hand is set, the spring is tripped and the tension is released, allowing the bell hammer to vibrate against the sides of the bell, creating a loud cacophony and (hopefully) waking you up.

Tracing the building blocks of a digital clock would be far beyond the scope of this article, but suffice to say that there are no springs and gears. Instead, digital clocks rely on electronics rather than mechanical machines to get the job done. Instead of a pendulum or an oscillating wheel, digital clocks use an electronic timebase to count off the seconds and keep the time accurate. Instead of gears, digital clocks use what's known as a "counter" and, of course, the clock uses an LED or LCD face to display the numbers rather than hands and a painted surface. For the alarm mechanism itself, digital clocks make use of either a radio or a recording of an alarm sound, which usually rings or pulses.