Intercepting audio signals for manipulation and processing

End Goal:
Prototype circuitry (and code) that can intercept and process audio signals from an intercom handset.

Background:
- An intercom handset has three main states. (1) Idle (2) Ringing (3) Answered
- When (1) --> (2), two separate audio signals move from 0V --> ~4.5V
- These signals need to be manipulated to lower voltages to move handset from (2) --> (3)
- When in (3), the signals will carry voice audio, so requires some work with ADCs to achieve requirements

Work done:
- I have already built proof of concept with RPi, Automation Hat
- I have oscilloscope and a number of ICs and tools that I think are suitable
- Just need help approaching the problem correctly

About me:
- Data scientist, so can code
- Limited understanding on electronics and audio however