Hi guys;
I would like to give my 2 cents here.
There goes. DTMF is numbers only. 0 to 9. ASCII is a an 8 bits code from 0 to 255 So let say that I what to send a letter A and the ASCII is 41 Hex --> 65 decimal, so you send tone for 6 and tone for 5, in this way, you can send a full ASCII text file over the "wire" and receive back like "de-tone" for 6 and "de-tone" for 5, so you have the number 65 and convert to ASCII.
My 2 cents