WARNINGDo not connect the pin directly to some sort of audio input. The voltage is considerably higher than a standard line level voltages, and can damage sound card inputs, etc. You could use a voltage divider to bring the voltage down, but you have been warned.You MUST have a resistor in line with the speaker, or you WILL damage your controller.
Which circuit is better to use?
however is requires a 33mH inductor,
which I have no clue where to find.
The volume got low enough that is was softer than the I didn't even need the capacitor!
The input circuit isn't working.
I did find that the output from the telephone is about 1.7 to 1.9 volts.
Is it worth it?
I just tested it again in AC. it stays at 0 and then goes up as I press buttons and talk into the other telephone.
When I press a button (a tone) it goes to 0.3 volts AC.