While you wait for answers, we may have found some information which could help you.
Click here for Studio 1100 Helptelephones?
bt 1100 twin need to replace broken 2nd handset?
How do I connect my own answering machine?
how can i fix a bt graphite 1100phone?
how to repair BT 3500 Studio phone base (Master) unit?
BT Studio 1500 triple set?