1.2 Making Calls
To answer the callback ringing from an idle outside line
While hearing a callback ringing
If you do not answer the callback ringing within 10 seconds, this feature will be cancelled.
To cancel callback ringing (Automatic Callback Busy Cancel)
Setting Callback on an ISDN Line (Completion of Calls to Busy
You can set the telephone to receive callback ringing when a busy called party on an ISDN line
When you answer the callback ringing, the called party's telephone number is automatically dialled.
While hearing a busy tone
Dial outside phone