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Thread: newbie's question about car alarm transmitting freqencies

  1. #1
    Constant Bitrate minghi's Avatar
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    newbie's question about car alarm transmitting freqencies

    ok, i dont have a car alarm installed, infact i never really understand how they manage not to screwup. i mean i observed that most alarms transmit signals at apprx 330Mhz.

    Now, how come one alarm does not open the doors of another car. say, if 1,00,000 people bought the same alarm module from the same manufacturer, is the probabilty of mismatch > 0? just wondering.

    also, if i buy a transmitter unit like http://www.partsexpress.com/pe/showd...number=330-145 can i program the alarm myself, like set the transmitting "key" code manually. \

    thanks
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    Constant Bitrate minghi's Avatar
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    Quote Originally Posted by joshthepilot
    For your reading pleasure...

    http://money.howstuffworks.com/car-alarm8.htm


    And no, you can't set it manually. It changes constantly and with a basic encryption. Don't you think that is a bit more effective?

    sweet.....thank you
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  3. #3
    Constant Bitrate csnowman00's Avatar
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    because the transmitters are very differant, like 1 in 1.3 billion are the same, i forgot the number. the alarm receiver is set up to use that unique transmitter. so dublicating that transmitter will be almost impossible.

    if you wanted to get into someone elses car (not saying you would, im just saying)...u would have access to their alarm and add your transmitter - its the only way
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    Maximum Bitrate kiltjim's Avatar
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    Looking at the system you posted, it doesn't say anywhere about rolling codes. You might be able to change the key. However, alot of them have the key permanently set.

    Some of them, (a system very similar to the one shown above, that I have worked with included) have jumpers to allow you to change the key. But, that one has the remote learning feature, so it can't have the jumpers in the base. It might have the jumpers in the remotes, but I doubt it. And speaking of the learning function, this also means that the remotes can't have rolling codes.

    If you are looking for something that allows you to change the key, you can still find the jumper based ones.
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