I am going to build a DTMF dialer (not only generator) project. I don't want to use any of the chips which makes the DTMF tones and simple interfaced on a uP.
I wrote the code that makes the DTMF, but my problem is how can I safety send the tones in the Line in order to make the call. I have seen a telephone uses a transformer in the line (Ok, I understand this).
Does anybody have any simple circuit without a DTMF generator chip (only an AVR) and the peripherals used for isolation and amplifiers for sending DTMF tones?
Thank you very much