While you wait for answers, we may have found some information which could help you.
Click here for Bt Studio 1100BT Studio 3500 base problem?
How do I connect my own answering machine?
how do i record a telephone conversation on a bt synergi 5500 cordless anse?
how to repair BT 3500 Studio phone base (Master) unit?
Bt 3500 cordless tel/answerphone?
BT Studio 1500 triple set?