I am not in your FTTP situation yet. But I do use V.O.I.P. adapters here plugged into my existing router. I decided to check what would happen if, and when, I required to lose my existing copper BT/Sky phone, by plugging in my wired phone system into one of my existing V.O.I.P. ATA's. All my wired phones worked, including an EXTENSION BELL! perfectly O.K. BUT I did need, in my case, to plug in a broadband filter to provide a bell wire to get some of the older telephones and telephone bell to work. For my test I used an old spare Grandstream 486 ATA, set up as a duplicate Sipgate line for my tests........