Todays useful motoring tip.

[Quicker]

actually a commerical for blue-tooth headsets!

[Jonathan]

LOL I was gonna say - a phone dishes out about 1 watt of RF at peak, when ever I've done that in the microwave it's been at 600w setting for about 2 minutes.

Crazy

[Roger 912]

I cannot believe that none of you have noticed that if your cell phone is in the car and your radio or cd is playing you often get a "diddle dum, diddle dum" over the speaker. This is the cell phone's transmitter getting into the audio part of the car radio. When you drive into another "cell" area, the receiver section picks up a new signal and the transmitter of your phone automatically replies. This happens also just prior to receiving a call.

Now, when the key ring transmitter be pushed, this 402 mHz rf signal gets in to the audio section of the modulator of the cell phone and the digital information is transmitted over the cell phone. This digital information being retransmitted by your cell phone can get into the demodulated section of the 402 mHz receiver in the car and operate the locks. Depending on the type of cell phone, some may be more prone to working with the key transmitter more than others. Try holding the key transmitter closer to the cell phone when trying and also try holding your cell phone closer to the locked car.

[Jonathan]

I can't believe you didn't read the thread

the effect is similar to when you call someone on a cell phone and hear normal voice, but move it towards a speaker and hear "derrrrdukderrrdukdukdukderrrrr" that is the raw signal coming into the phone, the phone is chaning that into comprehendable voice. The noise you hear on a nearby speaker is the RF being induced into the magnetic coil in the speaker.

The key fob doesn't 'speak' as such but the RF signal harmonic it gives off can be induced into the phone's carrier signal becuase the RF would get into the microphone circuit if held close enough (exact opposite of the "derrrrdukderrrdukdukdukderrrrr" effect) - that menas in theory the phone can be transmitting the code for the lock.

I reckon this does 'work' but as others have said only on certain phones and or certain alarm/c locking receivers where the code can break in.

If I could get a car that works I could put the frequency counter and spectrum analyser on it and so forth and actually see what's happening for real.

The reason why I am so interested is that implications of it working is that you wouldn't necesarily need the correct fob or the correct code to open the car or disable the alarm...