Is this myth or fact?

  Arthur Scrimshaw 18:11 12 Jul 2008
Locked

I was reading somewhere the other day that if you lock you car keys inside the car, you can use a mobile phone to unlock it?
Apparently it works like this - the car needs to have remote central locking and you must have a spare set at (for example) home. Call home and get someone to press the 'unlock' button of the spare set while holding them next to the home phone microphone, at your end you hold the mobile near to the car. This is supposed to unlock it. Has anyone tried this?

  GANDALF <|:-)> 18:12 12 Jul 2008
  Arthur Scrimshaw 18:22 12 Jul 2008

Thanks, thought it seemed too simple!

  Pineman100 19:07 12 Jul 2008

you can use a mobile phone to unlock the car. Here's what to do.

Simply call home and ask a member of the family to get hold of your spare remote beeper. Offer them £10/the latest Coldplay CD/dinner out/a big kiss (delete as appropriate) to drive or get a bus to your location.

Easy, eh?

  tasslehoff burrfoot 19:14 12 Jul 2008

I have a work colleague who claims to have successfully done this.

I showed her the snopes page, but she still maintains it worked.

  Fruit Bat /\0/\ 19:37 12 Jul 2008

Depends on the type of car - according to the AA man I was speaking to on Thursday.

  jack 19:42 12 Jul 2008

The required response f0r a central locking system is either Infra Red or Radio- two types.
A phone outputs Audio
Draw your own conclusions.

  Brumas 21:02 12 Jul 2008

Fascinating article, I shall trawl through the site at leisure.

  UncleP 23:47 12 Jul 2008

Interesting - the original thread asked if anyone had actually tried this (mythical?) system of unlocking a car door. Only one post, from Tasslehoff Burrf, refers to a practical test (I'm not sure how to interpret the comment from Fruit Bat) by a colleague who claimed that it did - and who remained resolute when challenged.

But the general attitude appears to be that it is unlikely in principle and therefore to be dismissed: so much for experimental science! The reference given by GANDALF states categorically that it can't work because the operating frequencies of a mobile phone and the car keys are different (although both are in the UHF range).

This strikes me as an extraordinarily simplistic argument; it makes no allowance for the fact that UHF circuits are generally broadband, and are likely to show some reduced response at harmonics and sub-harmonics of the nominal frequency. In addition, the power output from a mobile phone is considerably higher than that from car keys.

I'm not saying that I think it should work - there are other factors such as the type of modulation which would have an effect. But as Arthur Scrimshaw implied, a simple test will give a result; much easier than ploughing through circuit diagrams and specs. I can't run a test myself (the wife has written off the car, and my bike doesn't have remote locking), so it's up to you guys.

  laurie53 10:49 13 Jul 2008

Are you saying that if I operate my key fob within radio range of any mobile phone the frequency will then be transmitted to whatever number is being called, and will then be picked up by the car?

If this is the case I am surprised the local villainry have not developed a method of sitting in a supermarket car park with a mobile phone, recording all the frequencies they can, if only on paper, and then using a signal generator to nick the car at a later date.

  Bingalau 11:22 13 Jul 2008

I once vacated my car too quickly and immediately realised I had left the keys in the ignition, furthermore I had locked myself out. I was outside a police station at the time and was going to the local court for an occasional licence. When I came out of the court I asked in the police station if they had any way of opening my car door. Would you believe in the end one of them managed to open the door by breaking the small sidelight window with a sledge hammer. He had to really use a good deal of force too. Damn good car that VW.

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