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Circuit Troubles - Connecting DTMF Decorder to Phone Line

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New Member
Hi everyone

I was wondering if someone could look at the attached circuit and see if it looks ok, and will work for my application.

My application is too use an MT8880 IC (Controlled by a PIC MCU) too send and receiver DTMF signals. I know the Components attached too the MT8880 are correct(from data sheets) I am just unsure of how i am suppose to connect that IC too the phone line

I used a part of an schematic i found on the net and just wondering if anyone could look at it and see if i am missing anything, ie isolation. The parts that i am unsure of is the Transformer (or what type too use), what kind of relay i should use and why i need the 1N4148 diode(which i borrowed from someone else on the net).

Also, i am unsure of where i should attach a speaker too this system.

Any help on this matter would be great


lee Stoner

It is in Autocad .dwg format, if another type is required let me know


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