Hi Southpark,
Yes from my posts I mixed all of the terms. The frequency is not what I need, but at some point I have mentioned frequency also. Reason for that is that maybe I should look in that direction in order to write my code in a good direction. And yes this is AC signal and the tone that I hear is something like a turkey = )
I would guess somewhere at 2khz.
Thanks for the link for peak detector.
Thing is that I am assured that this is so easy once I grasp the concepts and the way of thinking in order to understand the logic.
I am not throwing away suggestions you are giving. This is not about interphone, the goal is programing.
And along the way if I can ease myself opening the door the merrier is the result of my learning.
I guess you understood what I want to do fully?