Electronic – Multiple DTMF circuit interfaced to one microcontroller, will it work


I already tested this circuit with only one modification, I changed the R2 to 300kOhms which worked in my case.
DTMF circuit

I interfaced this circuit to a microcontroller where they shared a common ground. I successfully read the telephone number of the caller as shown in this figure. Apparently, I received the code number (10 2) and the 7 digit phone number. The frame was encapsulated with byte 0 and byte 15.

enter image description here
Now, I wanted to create a circuit that contains 3 channels for 3 different phone lines which are then to be interfaced into one microcontroller..

If I'm going to share a common ground for them all (3 DTMF circuits and microcontroller circuit), will it work?

On the sidenote, based on the datasheet, the circuit is in single-ended configuration.

EDIT: I added the entire circuit shown below.
enter image description here

Best Answer

Yes, you certainly can have three of your DTMF decoder circuits connected to your microcontroller.

However, even though the three telephone lines nominally share the same ground (somewhere), you should really treat them as "floating" with regard to your decoders, and use a transformer to couple the audio from each line to the corresponding decoder.