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  1. #1
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    Default Anyone know anything about MDT or AVL or along those lines?

    I was thinking about different ways to make a 'police detector' and I realized that more signals are given out then just radar/laser and radio waves for talking. They have computers in their car that upload data constently to sites like http://cad.chp.ca.gov/ so there must be some sort of way to detect these things. I'm curious what type of waves are given out and at what frequency. Is it GSM or EVDO? I don't know if someone can use a scanner to locate where a phone is. I would love to learn about all of this even if it will not go anywhere.

  2. #2
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    The earliest MDT's used a RF modem, where there was a radio in the car, and also a base station in the community, that supported the data to the MDT's. This was prior to the cellphone system based data networks that exist in pretty much all of the populated areas today.

    Today's MDT and AVL systems could still use RF modems on a standard system, or also on a trunked radio system. They could use data on a cell phone based network (as you wrote, GSM or EVDO). In some cites they have built or are building WiFi or WiMax based wireless networks, or they partner with a business that wants to build the network in the area, to get coverage for their vehicles.

    The local transit agency uses RF modems on a conventional system, and if I program in the base freq, I heard a constant data stream. If I program in the mobile input freq, I can hear when a bus within a few miles transmits data.

  3. #3
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    on this page http://www.howstuffworks.com/cell-phone7.htm it says "In CDMA, each phone's data has a unique code."

    Does anyone know if the phone has a static code or is this unique code dynamic, as in the code is assigned when the call starts?

    I'd like to figure out a way to identify this code.

  4. #4
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    You can start reading here
    http://en.wikipedia.org/wiki/CDMA

  5. #5
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    I've read through that and more. If CHP use CDMA then they should be identifiable from other people on cell phones with a european scanner. The problem is some computer software would most likely have to be written to identify who is talking on a cell and who is an officer. Buying a scanner pci card for a computer would cost a lot, and then there is the learning how to program for it. I doubt it is in packets like the net. I don't know how the unique code is identified. *does more research*

    any idea how often cell phones broadcast pn code? http://en.wikipedia.org/wiki/Pseudorandom_noise If it is often enough that might be a way to identify who is who, but you need a key to identify who is who, soo.....


    I see why no one has been able to use a scanner to pin point where officers are via their computer links to hq.

 

 

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