With a 10v adaptor you will not be able to answer incoming calls,you will receive the NU tone. BT have been trying to resolve this issuev since August, mind you their techi guys in Delhi are unaware of this and just tell you to reconfigure, or re-boot the box. I have wasted hours on this, in fact the last last e-mail I received from them i have put below, they talk absolute rubbish.
"Please accept my apologies for the inconveniences caused to you in this matter. I see that you have issues in BT Broadband Talk service which is enabled by 10V adapter. You have reported this to our BT Broadband Talk technical helpdesk which is not yet resolved. Unfortunately, the BT Total Broadband Helpdesk only deals with issues related to BT Total Broadband. The issues with BT Broadband Talk are dealt by a dedicated BT Broadband Talk department.
If you provide us with a convenient date and time (between 09:00 hours and 21:00 hours, BST) we will contact you and transfer the call to them. They will be able to provide you adequate information in this matter. I can also provide an alternate solution in this matter if you have both wireless router and BT Voyager 220v router. You can use one to access the Internet wirelessly and another for BT Broadband Talk service.
To perform this setup your premises need to have at least two sockets so that you can connect two routers. To perform this, please contact our Home IT Advisor on the number 0800 169 0024. They are expertise to provide assistance in this matter. The service offered by them is a paid one. To get information in this matter, please visit the link given below:"
Even the phone number they have given is no longer in use