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[Rob James]

I don't know if any of you have seen the email doing the rounds at them moment about opening your car with your mobile phone?

Basically you stand by your car with your phone, ring someone who has another set of keys (as you have locked yours in your car). This person presses the unlock button on the key and this transmits the signal from their mobile phone to yours, your phone then transmits the signal and it unlocks your car! See http://www.wsdmag.com/Article/ArticleID/13453/13453.html

We didn't believe it at work so we tried it, and it works (only mobile to mobile). Anyone have any ideas how this works?

[Kevin Wood]

I really don't believe it does work. I have worked on the signalling stacks used in mobile phones for 16 years and there is no mechanism by which it can "relay" the output of the key fob to another mobile.

How far away was the fob when you tried this? Does it work if it's a mile or two away?

Kevin

[keith2.2]

I don't believe this for one second - it assumes that for whatever reason, the 'transmitting' mobile phone would pick up a frequency from the keyfob and see fit to piggyback it through the transmitters.

still, I'm going to try it for sh*ts and giggles  

[tmx]

I work for a leading telecoms company

i have a comprehensive understanding of how voice is transmitted via radio on mobiles and on landlines

mobiles use a 9.6k this is preety bad which is why you can tell the differnence in voice on mobile vs landline mobiles also use TDMA which mean when you stop talking the network closes the cct down for a milisecond to save bandwidth on the cell

it wont work simple as that not even over a 64k pstn line the signalling mobiles use is designed to carry voice and can handle data but barely!!!

[Timbuk]

Did an expreriment on the TV the other week and it just did not work

[Bo Bo]

Did an expreriment on the TV the other week and it just did not work

You were on TV?  

[Rob James]

I was very sceptical, but I assure you it worked! When I read it I dismissed it out of hand, but one of my colleagues persuaded me to give it a go.

The only thing I can think of is that the aerial picks it up, encodes it, sends it across the mobile network and the the receiving phone decodes and transmits it. I don't know if it will work for all cars, or even with all mobile phones. One thing I did find was that I had to press the key fob a couple of times. I suggest you give it ago and see what happens (if you can find a willing volunteer to help you!).

[Kevin Wood]

I was very sceptical, but I assure you it worked! When I read it I dismissed it out of hand, but one of my colleagues persuaded me to give it a go.

The only thing I can think of is that the aerial picks it up, encodes it, sends it across the mobile network and the the receiving phone decodes and transmits it. I don't know if it will work for all cars, or even with all mobile phones. One thing I did find was that I had to press the key fob a couple of times. I suggest you give it ago and see what happens (if you can find a willing volunteer to help you!).

That would require a dedicated transceiver in side the mobile at the key fob frequency of 433 MHz (there are several others too, 418, etc...) and also an infrared transceiver compatible with the fobs in case you've got an old style fob. It would require software to decode and recode the key fob signal and also some means to transfer it between the phones. I can assure you that none of this exists inside a mobile phone.

As has been mentioned a speech coder is used to transfer speech from mobile to mobile and it has no provision for multiplexing in this type of data in with the speech.

Kevin

[tmx]

its not a speech coder its a timeslot on a 2mbit that gets sent through a voice switch and sent on its route through the operators transmission bearer network C7 signalling info would also have to be modified in order to carry this data and theres no chance that it has been set up to do it you would have to have some serious kit to transmit a 433mhz signal via a wireless speech path

my opinion is its nonsense

[Entwood]

its not a speech coder its a timeslot on a 2mbit that gets sent through a voice switch and sent on its route through the operators transmission bearer network C7 signalling info would also have to be modified in order to carry this data and theres no chance that it has been set up to do it you would have to have some serious kit to transmit a 433mhz signal via a wireless speech path

my opinion is its nonsense

I totally and wholeheartedly agree !! ( what with I have no idea !!    )

[cem_devecioglu]

the conversations in the link is really funny  

[Richie London]

wasnt there a watch a while ago that used to be able to pick up on car alarm signals, it also changed tv channels too. casio i think it was

i had a mobile  a few yrs ago that used to be able to run the bath for me and get the dinner on the table when i sent a text to a certain set of 11 digits.    


richie

[Kevin Wood]

the conversations in the link is really funny  

Yeah, you're right, actually.  

This one was good and to the point, I thought:

Can you hear the signal from your key fob? Does your keyfob make a sound?

NO is doesn't therefore it is not generating a sound wave, therefore the microphone cannot pick it up and cannot turn it into a signal that it can generate and send!...how hard is that to comprehend?

 

Kevin

[Kevin Wood]

wasnt there a watch a while ago that used to be able to pick up on car alarm signals, it also changed tv channels too. casio i think it was

Casio PC-Unite? I had one for a while. Got fed up with it cos it was so rather hard to tell the time let alone do anything else with it.

i had a mobile  a few yrs ago that used to be able to run the bath for me and get the dinner on the table when i sent a text to a certain set of 11 digits.    


richie

Yeah, I've got one of them. Not very reliable though. Every so often it seems to throw a hissy fit and then the voice activation fails for a couple of days. Seems to do this about every 28 days... :-/

 

Kevin

[Rob James]

I agree completely, as far as I can understand it shouldn't work - however having tried it and seen it working I know that it does work.

the conversations in the link is really funny  

Yeah, you're right, actually.  

This one was good and to the point, I thought:

Can you hear the signal from your key fob? Does your keyfob make a sound?

NO is doesn't therefore it is not generating a sound wave, therefore the microphone cannot pick it up and cannot turn it into a signal that it can generate and send!...how hard is that to comprehend?

 

Kevin