How Does a Car Key Chain Unlock/lock a Car? By Ben L. 2011
Have you ever ridden in a car? Have you ever seen somebody lock a car by simply pressing a button? Most people have seen it at one time or another. Today you will learn about how this amazing contraption works.
What is electromagnetic radiation?
Electromagnetic radiation is, in simple terms, a humongous spectrum of energy. There are seven types of electromagnetic radiation. The seven types are Radio Waves, Microwaves, Infrared Radiation, Visible Light, Ultraviolet Radiation, X-Rays, and Gamma Rays. The type of electromagnetic radiation that you are learning much more about is infrared radiation.
The chart above shows different types of energy on the electromagnetic spectrum.

What is infrared radiation?
Infrared radiation is a type of light on the electromagnetic spectrum. Infrared radiation is also known as radiant heat. Short wavelengths of infrared energy can be absorbed by many kinds of matter and can warm the things it falls on. Longer wavelengths of infrared radiation pass through clouds of water vapor and/or dust. Infrared radiation is produced by vibrations and rotations of atoms and molecules and the motions of their electrons.
One example of infrared radiation is the way a remote control for a TV works. You will find out more about this type of concept in the next paragraph.
So how does the car key chain work?
Basically, when you press the lock/unlock button, infrared radiation waves are sent to the car. The car then catches the signal and locks or unlocks.
Here is a picture of a car key chain.

Here is a diagram about how the key chain works.

The reason that the key chain does not perform the actions on other cars, however, is very complex. Inside of the key chain, there is a 40 bit code that matches the code in the car. When you press the lock or unlock button on the key chain, the key chain sends directions to the car. If the code in the car matches the code on the key chain, the directions are followed. Most of this is done through infrared radiation.
Next time you see a car, remember how the key chain works. It is really an unbelievable contraption!

Electromagnetic Radiation: Radiation made of electromagnetic waves, such as radio waves and infrared radiation.
Spectrum: The whole range of wavelengths of electromagnetic radiation.
Infrared radiation: A type of light on the electromagnetic spectrum. More information in “What is infrared radiation?” section.
Radiation: The release of energy in the form of electromagnetic waves.

Citations: Brain, Marshall. Marshall Brain’s More How Stuff Works. New York: Wiley Publishing, 2003. Print.
Porter, Alison, Eryl Davies. ed. How Things Work. New York: Barnes and Noble, 2003. Print.
"radiation." Compton's by Britannica. Encyclopedia Britannica Online School Edition. Encyclopedia Britannica, Inc., 2011.Web.23 Sept. 2011.