Keyless entry and mobile phones

[sahilm]

Yes, I'm talking about the using-mobile-to-open-car-door thingy. For the uninitatated, rumour has it that you can open your car door by calling someone who has your remote key. He then trasmits the signal over the mobile network while you keep your phone in front of the car door.

I've seen several people vouch that it works. Both on this forum and in person. Personally i feel it cannot work because :-

1. The mobile microphone doesn't have the range to pick up
microwave signals transmitted by the remote.
2. Even if the microphone does pick up the signal, the filtering circuits in the mobile will filter it out(the mobile is designed to transfer audible frequencies).
3. Even if the signal isn't filtered out, mobile transmission are modulated in such a way that transmitted microwave doesn't go through.

Sadly, my knowledge of electronics is severely limited. Personally I would love to see Yoda's(Sangram's) take on this. I'm hoping he will put all my doubts to rest.

I'm sure there will be several people here, who will retort, "It works j00 n00b". Their replies are welcome as well.

I'm just waiting for Yoda to speak.

 

[pathik]

Is it totally operated by sound? Don't you have to atleast roughly point it in the car's direction. I mean, then could we just record the sound and play it? That wouldn't be very secure right?

 

[sahilm]

Is it totally operated by sound? Don't you have to atleast roughly point it in the car's direction. I mean, then could we just record the sound and play it? That wouldn't be very secure right?

Keyless entry doesn't work by sound. It works by microwave/radio waves.
Channel frequencies keep cycling so no, you can't record the wave and replay it.

 

[YoGi-Sama]

I have yet to try it myself, but yes... few of my friends have said that it works. I'm not sure if they really tried it themselves or just being blabbering bums.

Really would like to know the facts on this. Too bad my car doesn't have electronic locks, else I could have tried it myself, or maybe I should one of my friends who been saying that it works...

 

[greenhorn]

snopes.com: Cell Phone Unlocks Keyless Cars

 

[sahilm]

snopes.com: Cell Phone Unlocks Keyless Cars

I read that. Point is, people still claim it works. I want a definitive technical answer.

 

[vrd]

I read that. Point is, people still claim it works. I want a definitive technical answer.

from the same page greenhorn mentioned:

Remote Keyless Entry Systems Overview - Maxim

HowStuffWorks "How Remote Entry Works"

 

[sahilm]

from the same page greenhorn mentioned:

Remote Keyless Entry Systems Overview - Maxim

HowStuffWorks "How Remote Entry Works"

The above doesn't explain my question. I already know that keyless entry uses radio waves and cycling frequencies.

God of War and Hacker claim that it works, http://www.techenclave.com/general-talk/stupid-things-to-try-your-phone-123036.html.

 

[greenhorn]

the only situation where it would work if the lock was activated using DTMF sound or something. not done these days.

 

[sahilm]

Where are god of war and hacker?

 

[HailStonE]

It does not work.... seen it on Discovery last month where the guy showed it practically & failed hence concluded... Its only a rumor..... :rofl:

 

[cranky]

Theoretically, it's possible, if the to mobile phones had earpieces and microphones capable of listening to and reproducing the range in which the controller transmitted its signal (usually, a little above the FM radio band).

Practically however, this cannot be done by this method - primarily because of speech filters used to compress phone signals. If signal modulation techniques are used, it may be a particular set of remotes and locks that could be tampered with.

I have heard it is possible. I don't have a keyless system, and I'm not too keen on studying the phenomenon. It may be urban legend, again it may be demonstrated on a limited set of devices. That is not conclusive, so while I won't dismiss it out of hand, I won't accept it as gospel either.

 

[sahilm]

3. Even if the signal isn't filtered out, mobile transmission are modulated in such a way that transmitted microwave doesn't go through.

Thank you, Yoda. Is pt. 3 accurate?

 

[cranky]

Pretty much. It's like how you have certain cordless phones that you can hear on FM, but most can't.

Who's Yoda? Somebody from Star Wars? My name is Sangram, you know. My parents toiled a lot to give me that, so please do use it

 

[Gannu]

Who's Yoda? Somebody from Star Wars? My name is Sangram, you know. My parents toiled a lot to give me that, so please do use it

:lol: :lol:

On topic, it works for some though. Surprisingly it did for my friend's car.

 

[greenhorn]

how far was the actual remote from the car?

did you do a control test with the remote at that distance ( without the mobile) ?

 

[Anish]

Which car was it?

 

[vrd]

well maybe it works on some cars or cell phones,..but i wont believe it till it see it.

 

[sahilm]

Which car was it?

How does that matter?

 

[F-0ccY]

One technique that DOES work is the bheja keyless entry range boost