Hello Pasosh,
Did you find a sollution for your problem here? It is almost 12 years later since you started this topic... As I'm looking too for a schematic diagram for building a doorphone , connected to a phoneline. Generating a number and take the hook off isn't a problem , it is easy build with an AVR controller. For me the problem is to have a decent microphone amplifier , connected together with the loudspeaker amplifier and then connected to a 600 ohm transformer. As when the microphone pics up some signals , it would be advisable not to amplify these sounds then and yet , they both need to be connected together to reach the telephone line. Can you help me here?
Many thanks,
Ron1406,