I want to use a DTMF decoder IC such as HT9170 to get the numbers. What confused me is how to connect the decoder with telephone line? Is the transformer necessary? Or can I have another solution? What=92s the means of the =93600-600 Ohm=94 marked with the transformer? Thank you very much!
For a hobby project or will you be selling this? The transformer or capacitor solutions will suffice for a do-it-yourself project. But if this has got to be of professional quality, I'd suggest looking up the requirements for the interface requirements. Also, consider the that requirements will differ between countries in which you intend to sell this.
I saw 'China' in your email address, so I'm assuming that whatever solution you choose may show up in millions of consumer products sold worldwide any time now. :-/
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Paul Hovnanian paul@hovnanian.com
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