SO that means i need a seperate dialer chip than the TEA which will generate the DTMF tones which i will feed in the DTMF pin. i found one such chip at

http://www.kmitl.ac.th/~kswichit/dtmf/dtmf.htm


Please have a look at this, okey they have used a transformer for a direct link to the telephone line. can you explain this and what is the advantage and disadvantage of using transformer instead of the chip.

so i will need another chip for DTMF detection i mean if the B-Party presses any key on his telephone pad and if i want to receive that key press, i will need another DTMF detection chip or i hope the TEA provides such facility.


now on the last how can i replay the message when the connection is made. i mean okey i have to feed the message on the DTMF pin of TEA. ISD is one approach to do so(i still have to find out the interface for the DTMF pin and the ISD output). my question is what other approaches are there to do so with microcontroller.


Shahzad