While you wait for answers, we may have found some information which could help you.
Click here for Cordless Phone Register Telstra
telstra 6100a with 4 handsets?
How can I add a handset to telstra v580a?
Telstra 7100A, "Not Registered"?
telstra 8950a?
My cordless phone says Base 1 (Telstra 7100) ?
Telstra cordless 6100a Won't make calls?