> People can still have their analog phone directly connected to the socket in their house but now their call will be a VoIP call. Not sure where the transition

> People can still have their analog phone directly connected to the socket in their house but now their call will be a VoIP call. Not sure where the transition from the analog signal to VoIP happens, but I guess it's a the end of the customers copper line. The transition happens at the telephone exchange, or possibly occasionally in a FTTN/FTTC outdoor cabinet. And it only works that way if you're really only using a plain phone line without internet access. Otherwise, the transition needs to happen in your router.