Modern AVM Fritz!Box(es) cater for multiple incoming phone numbers. These can then be allocated to specific handsets and calls to a given number routed to just the corresponding handset.
This is quite a commonly used feature in Germany since telcomms are moving away from ‘physical’ landlines to digital ‘landlines’ delivered over the braodband signal.
Unfortunately, the current call monitor integration doesn’t allow the limiting of notifications to one specific number or hanset(s). This means that the call monitor currently displays data for incoming calls on any/all incoming lines.
Again, in Germany it’s common for families to have multi-generational homes that share broadband and allocate the number to specific dwellings within the same building. As a result the current implementation of Call Monitor is unusable since it blanket notifies of all calls regardless of who the call is being received by. It really needs to include an option to observe call data for a specific handset/incoming number only.