Connection to Feller door chime 230V, instructions from Netatmo: Please disconnect your brown wire from the chime and insulate it. Then place a wire between L and the pin where the purple wire is connected to your gong. Leave the purple wire where it is now wired. Finally, place the bell module between N and L on your gong. You should set your chime to High before switching it on. After making any changes, please reset.

It's been three years, but I'll add my two cents anyway. I've had the Netatmo for about two years and it's never really worked that well. Sometimes it rang, but often it didn't and the camera kept disconnecting. I've had enough now and bought the adapter for direct 220V -> 12V to camera. I replaced the Feller bell with a socket and Ring Gong.
Since then the connection has been stable, no more disconnects and there's a flow via the Smarthome that makes the chime ring when someone rings.
Super stable and always works.

I also had a Feller door chime, standard (230V). I hung the black module in between the gong and set it with the switches according to the instructions and then adjusted it. It actually works very reliably. Only the WLAN reception is a bit critical because of the aluminium door. Otherwise very practical.