Hi George,

I am sorry I didn't explain my problem the right way. Let me put it again.

I said "during the call progress", this means not the CP mode.

The problem is when It is receiving a call from outside, in DTMF mode and IRQ selected, if I press a button on an extension on the same line it can detect the DTMF tone by lowering the IRQ pin. It detects as many time as I press local set buttons.

But during the same call going on, if the remote caller person presses some button on his set then I can though hear the tone on my extension but the 8880 does not detect it, (no change on IRQ). I have even tried by disconnecting the extension and leaving only the 8880 connected to the line.

During the above problem it is only in the DTMF+IRQ mode whereas the Call Progress CP mode is never selected.

Sorry I confused the problem with call progress mode.

I am using single ended input configuration with a transformer taken out of a modem

Kindly now refer to my problem again and help.

Regards

Simon


PS:

I have already successfully used MT8870 in another application, where I used the differential input configuration.

How can I use the differential input with 8880 whereas I also have to connect the tone output to the line.

Can I do that by splitting the input and output, means I use differential input and use transformer for tone output or some other tele line tapping technique to throw the out put tones on the tele line. ????