DanielD You are right, very confusing, there is still an analogue phone connected which can still make outgoing calls so there is still a telephone line. I thought this check mark just disabled inbound calls but apparently not. Anyway I tested again today and outgoing calls could still be made, I suspect that making an outgoing call did something in the IB because now, whether I have incoming calls enabled or not there is no extra tick box saying “incorrect”. Perhaps I need to reboot the IB but I think it is more likely some sort of bug somewhere and I may never see it again.