Those chimes are directly connected to the transformer, using 2 of the wires. The other 2 wires are connected to the push-button.
They work like 2-wire chimes, except they have separate power- and switch-connectors.
Digital chimes, playing melodies might use this type of wiring to assure the music gets played all the way to the end, even after the push-button got released.
To connect the Netatmo Doorbell to that kind of chime, you need to rearrange the existing wiring on the chime's site:
- Switch off the power.
- Disconnect the 2 wires, going to the push-button and use a piece of wire to bridge the 2 now empty contacts on the chime.
- Disconnect the live-wire from the chime and replace it with one of the wires going to the push-button.
- Connect the now free live-wire to the remaining wire, going to the push-button, using a terminal.
- You also have to replace the old push-button with the Netatmo Doorbell and connect the Chime-Module to the 2 contacts of the chime, that are not connected together by the bridge wire.
For a better understanding, I didn't change the color of the push-button wires.
This way, the Netatmo Doorbell is fully functional and the chime only receives power when the button gets pressed.
Note: If you have a digital chime, playing a melody, that music will be cut-off when the button gets released.
This is a work around to keep the existing 4-wire chime in use but replacing the chime by a 2-wire model would be recommended longterm.
Side note: I'm not a Netatmo employe, I'm more like a freelance forum janitor who likes helping people with wiring stuff...