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