Wireless Systems Design

What Wireless Mystery?

I received a great deal of mail related to the wireless mystery I posed last month. As you may recall, the mystery was to figure out how to open your car door if you locked your keys in (see "Locked Your Keys In The Car? Get Out Your Cell Phone"). Using your cell phone, you call someone with an identical remote keyless entry key fob. Then you place your cell phone near the door lock and have the remote person press the key fob while holding it up to the phone. Magically your car door should open. I tried it and it did work. And many others tried it with the same results. I don't think anyone actually solved the mystery, but there was some interesting speculation.

A good number of readers pointed me to snopes.com. The snopes analysis basically says that the car may unlock not via the cell phone, but because the spare key fob is within range of the car receiver.

When most people try debunking this wireless mystery, their car is nearby. So when they push the button on the key fob, the RF reaches the car receiver directly (not via the cell phone). Makes sense in my case, but I am impressed at the range of these devices. In my case, the range was several city blocks through walls. Impressive.

In any case, I still have to wonder if there is another answer out there. A couple of readers suggested some alternatives. One even tried to put a spectrum analyzer near the receiving cell phone to try and figure it out. No clear results were noted.

Anyway, this whole thing made me think about how much time we waste on stuff like this from the Internet. I heard of this mystery via the Internet, and I suspect the person who sent it to me got it that way as well. And, the answer referenced above came from the Internet. Is it really true? I guess.

What I come away from all this is: Try not to believe everything you read, especially if you get it on the Internet. Except for this newsletter, of course.

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