On your key chain there is a miniaturized computer system. It's the electronic key fob that opens your car door. Though small in size, the fob does a big job to keep your car secure. When you push the button, your fob sends out a radio signal that can travel several hundred feet. A hundred cars might be in the range of your fob's radio signal, but they'll all see your fob's signal and ignore it. Only your car is going to respond to your key fob.

If each key fob has a unique serial number programmed into it, then it can send out that serial number as part of the radio signal. The computer in the car could receive the signal, look at the serial number and unlock the doors only if the serial number is correct.

A serial number like this would work fine, except for one problem: Criminals would be able to sit in the parking lot with a radio scanner and capture the serial number. They would later be able to retransmit your serial number and get into your car.

To solve this problem, engineers developed something called a rolling code transmitter. The transmitter in your fob sends a different random number every time you push the button. The number your transmitter sends today will open your car, but the next time that number is used, it won't. Now, if criminals try to capture your fob's transmission, the number they capture doesn't do any good. The number is only good one time.

But if your fob sends a different random number every time you push the button, how does your car know it is the  correct number? The fob and the car are both using the same random number generator.

But the rolling code system does create another problem. What if you press the button on your fob and you are nowhere near your car? Or what if your kid gets hold of your fob while you are inside the mall and presses the button 10 times for the fun of it? Now the fob's random number will be different from the one that your car expects.

Engineers solve this problem with something called look-ahead. When your car sees a random number come in from your fob, it looks at the next 256 numbers in the random number sequence. If it sees any of those 256 numbers, it will unlock your car.

So what happens if your child gets hold of your fob and presses the Âbutton 500 times? Your car will ignore your fob. You must then re-synchronize your fob with the car. Your owner's manual includes instructions on how to do this.