I have purchased an intercom ring and have carried out the installation according to the app for a Fermax 8039 citymax, I think everything is fine, I have attached an image of the wiring carried out. Everything works correctly except for the microphone of the street intercom, in which you can hear a continuous and annoying noise but not the voice of the speaker. In the other direction phone --> street does work. Also the door opens correctly. Where could I be in error? I don't know if it's a problem with the installation or the device.