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  1. #1
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    DTMF decoder MT8870 for mobile phone

    Dear forum,

    Hope you are doing well.

    I have been working with the DTMF decoder MT8870 for few months but i could not get success. I have used few circuits mentioned in the datasheet. But i am facing problem *, 0, # , 7, 8 ,9 buttons are working but sometime works the 1, 2, 3, 4, 5, 6.

    Why is that???

    I have connected to MT8870 Pin 2, 3 ....> 100 Kohm

    But one thing i need to ask i have took dtmf toon from the mobile phone T68 speaker and connected to the MT8870 using a 5Kohm Variable resistance to control gain.

    What is the working cirucit for the mobile phone.

    Waiting for your supportive response.

    Regards
    Shan

    •   Alt15th February 2009, 13:56

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  2. #2
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    Re: DTMF MT8870 Decoding

    try it.....
    To get good result use nokia 6600 with docomo/bsnl(in India)sim in decoder side.
    by Ur,
    sree

    ---------- Post added at 09:51 ---------- Previous post was at 09:46 ----------

    try another one

    ---------- Post added at 10:00 ---------- Previous post was at 09:51 ----------

    try it.......
    Circuit diagram shown in http://images.elektroda.net/55_1286856678.jpg

    please try 8.2k and 82k in the place of 8.2k resistor(marked in the image).To get good result use nokia 6600 with docomo/bsnl(in India)sim in decoder side. it worked with me
    by Ur,
    Sree



    •   Alt12th October 2010, 06:30

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  3. #3
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    Re: DTMF MT8870 Decoding

    i made such a this circuit that you made. ihad some problems like you. And i took off the microphone of mobile phone. because the the signals that came from the microphone and keyboard of the mobile phone could mix. so it causes stability problems in your circuits. Try it and send me result. have a good works



    •   Alt12th October 2010, 08:29

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  4. #4
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    Re: dtmf mt8870

    check this site a for a project called dtmf device control using micro controllerFREE PROJECTS ON HARDWARE(8051) AND SOFTWARE(VB, C,C++,JAVA...).

    make sure u using original dtmf decoder ic. cheap ic's doesnt respond well for some buttons. nokia phone works well. i didnt get satisfied results in samsung phones and one with usb connectors



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    Re: DTMF decoder MT8870 for mobile phone

    Hi! I've built a poroject with the mt8870 and I've connected the Q1-Q4 outputs to LEDs so that I can see the codes, but when I call too the phone line by my Nokia 5800 and it would got busy, but the dtmf decoder doesn't seems to work :) any idea?:)



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    Re: DTMF decoder MT8870 for mobile phone

    Rajsekhar Nag
    -------------..--------
    Knowledge Grows When Shared



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