Setting up FRITZ!App FonFRITZ!App Fon allows you to conveniently make telephone calls over the FRITZ!Box with your smartphone when you are at home – the smartphone functions as an IP telephone. You can also use FRITZ!App Fon with several FRITZ!Boxes and thus make calls over different FRITZ!Boxes. For this you must set up FRITZ!App Fon once on each FRITZ!Box as described here. After setting it up,...
> https://en.avm.de/service/knowledge-base/dok/FRITZ-Box-7690/251_Setting-up-FRITZ-App-Fon/
Mesh with FRITZ! Whether it's a large apartment, house with several floors, or a spacious garden – sometimes the FRITZ!Box's Wi-Fi network alone is not enough to seamlessly cover every single corner of the home with Wi-Fi. Not only long distances, but also impenetrable walls and interference-causing materials can affect the Wi-Fi signal so that it barely reaches or does not reach some rooms. So...
> https://en.avm.de/service/knowledge-base/dok/FRITZ-Box-7690/3329_Mesh-with-FRITZ/