# Cellphones and key fobs **URL:** \ **Category:** Factual Questions\ **Created:** [September 27, 2006, 2:55pm UTC](https://boards.straightdope.com/t/cellphones-and-key-fobs/374365 "2006-09-27T14:55:06Z")\ **Posts on this page:** 11\ **Page:** 1
**Author:** ![Improv\_Geek](https://avatars.discourse-cdn.com/v4/letter/i/b3f665/32.png) [@Improv\_Geek](https://boards.straightdope.com/u/Improv_Geek)\ **Post date:** [September 27, 2006, 2:55pm UTC](https://boards.straightdope.com/t/cellphones-and-key-fobs/374365/1 "2006-09-27T14:55:06Z")
Originally I came across this here: [http://www.wsdmag.com/Article/ArticleID/13453/13453.html](http://www.wsdmag.com/Article/ArticleID/13453/13453.html) Has anyone tried this? I had always assumed cell phones were mp3 like and filtered the ranges they transmit to make the transmission smaller, but if this works I must be wrong. I tried an off of it by attempting to record the key fob with my phone’s voice recorder, that didn’t work. – IG ---
**Author:** ![CookingWithGas](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/cookingwithgas/32/485_2.png) [@CookingWithGas](https://boards.straightdope.com/u/CookingWithGas)\ **Post date:** [September 27, 2006, 3:59pm UTC](https://boards.straightdope.com/t/cellphones-and-key-fobs/374365/2 "2006-09-27T15:59:31Z")
:rolleyes: Everything I have read about this, including Snopes, says this is a myth. Key fobs use RF (radio signals) and a cell phone cannot pick up and retransmit a radio signal from an external source. I am highly skeptical that this person did what he said he did. The author did not describe exactly how he did it (What were the locations of the two phones being used? Which end was he on and who was on the other end? Where was the car in relation to the two phones?) Snopes sez: > [@](#): > > More than a few people have inadvertently fooled themselves into believing the cell phone method of unlocking car doors actually works because they tried it and achieved the desired results — not realizing their cars were still within range of their keyless remote devices, and the signals that unlocked the doors were transmitted the usual way [i.e., through the air], not via cellular phone connections. ---
**Author:** ![CookingWithGas](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/cookingwithgas/32/485_2.png) [@CookingWithGas](https://boards.straightdope.com/u/CookingWithGas)\ **Post date:** [September 27, 2006, 4:01pm UTC](https://boards.straightdope.com/t/cellphones-and-key-fobs/374365/3 "2006-09-27T16:01:46Z")
[QUOTE=Improv Geek] . . . I had always assumed cell phones were mp3. . . I tried an off of it by attempting to record the key fob with my phone’s voice recorder, that didn’t work. [/QUOTE] To elaborate, the key fob does not emit any sound that you can record, it sends a radio signal. And last, the claim is that you can send the signal from one phone to another, not record it. ---
**Author:** ![Improv\_Geek](https://avatars.discourse-cdn.com/v4/letter/i/b3f665/32.png) [@Improv\_Geek](https://boards.straightdope.com/u/Improv_Geek)\ **Post date:** [September 27, 2006, 4:39pm UTC](https://boards.straightdope.com/t/cellphones-and-key-fobs/374365/4 "2006-09-27T16:39:22Z")
Thanks ---
**Author:** ![Baffle](https://avatars.discourse-cdn.com/v4/letter/b/dec6dc/32.png) [@Baffle](https://boards.straightdope.com/u/Baffle)\ **Post date:** [September 27, 2006, 5:12pm UTC](https://boards.straightdope.com/t/cellphones-and-key-fobs/374365/5 "2006-09-27T17:12:55Z")
Your link doesn’t work, and I can’t use Snopes’ search feature succesfully. ---
**Author:** ![Baffle](https://avatars.discourse-cdn.com/v4/letter/b/dec6dc/32.png) [@Baffle](https://boards.straightdope.com/u/Baffle)\ **Post date:** [September 27, 2006, 5:15pm UTC](https://boards.straightdope.com/t/cellphones-and-key-fobs/374365/6 "2006-09-27T17:15:13Z")
Er… **CookingWithGas** , your link. ---
**Author:** ![corkboard](https://avatars.discourse-cdn.com/v4/letter/c/e9bcb4/32.png) [@corkboard](https://boards.straightdope.com/u/corkboard)\ **Post date:** [September 27, 2006, 5:42pm UTC](https://boards.straightdope.com/t/cellphones-and-key-fobs/374365/7 "2006-09-27T17:42:49Z")
[Here’s](http://www.snopes.com/autos/techno/keyless.asp) the Snopes link. I call BS on the article claiming that it’s been done. Of course, I never tried it, but it just smells bad. ---
**Author:** ![groman](https://avatars.discourse-cdn.com/v4/letter/g/73ab20/32.png) [@groman](https://boards.straightdope.com/u/groman)\ **Post date:** [September 27, 2006, 6:42pm UTC](https://boards.straightdope.com/t/cellphones-and-key-fobs/374365/8 "2006-09-27T18:42:17Z")
Basic googling is leading me to believe the key fobs use 260-470MHz transmissions of digital unlocking codes. The US frequency appears to be standardized at 315MHz but I’m not 100% sure on that. I’m not an EE but I would guess it would be extremely unlikely that this would ever work like described? What mechanism would explain such behavior? I suppose an analog cell phone tower with bad filtering that uses a base frequency of 315Mhz or a higher harmonic could accidentally pick up the keyfob digital signals as part of your analog call, effectively modulating the keyfob signals on top of your audio. When transmitted to the other end the car would react to the signal incoming on that frequency and somehow ignore the noise of your call. :dubious: This would require so much unobtainium, unexplainium and things-just-don’t-work-like-that-anium that it’s not even meaningful to consider which analog cell phone standards use 315Mhz or a harmonic (I can’t think of any) . ---
**Author:** ![brewha](https://avatars.discourse-cdn.com/v4/letter/b/91b2a8/32.png) [@brewha](https://boards.straightdope.com/u/brewha)\ **Post date:** [September 27, 2006, 7:04pm UTC](https://boards.straightdope.com/t/cellphones-and-key-fobs/374365/9 "2006-09-27T19:04:22Z")
Unless someone tries it before 5:00, I’m going to try it when I get home. No use speculating on such an easy experiment. I’m almost certain it won’t work, but there’s no harm in trying ---
**Author:** ![brewha](https://avatars.discourse-cdn.com/v4/letter/b/91b2a8/32.png) [@brewha](https://boards.straightdope.com/u/brewha)\ **Post date:** [January 16, 2007, 7:23pm UTC](https://boards.straightdope.com/t/cellphones-and-key-fobs/374365/10 "2007-01-16T19:23:18Z")
Mmmmmmmm. Braaaaiiiinnnss. Ok, I know this a borderline zombie thread, but I just wanted to finally report my results. I just tried it last weekend and surprise - surprise it doesn’t work. We tried three different cars and nothing happened. I just wanted to make sure you guys could sleep at night. ---
**Author:** ![Rick](https://avatars.discourse-cdn.com/v4/letter/r/9f8e36/32.png) [@Rick](https://boards.straightdope.com/u/Rick)\ **Post date:** [January 16, 2007, 8:31pm UTC](https://boards.straightdope.com/t/cellphones-and-key-fobs/374365/11 "2007-01-16T20:31:24Z")
> [@](#): > > Unless someone tries it before 5:00, I’m going to try it when I get home.(09/27/06) > [@](#): > > just tried it last weekend (01/16/07) You win the longest commute on the SDMB award. Damn!