AASTRA 4420 IP Basic (SIP) for MX-ONE User Guide - Manual (Page 21)

21 Dialog 4420 IP Basic
Outgoing Calls
Callback if all lines are busy
If all external lines are busy (after dialing the digit or digits to get a
line): 6
Press
or Ô
Callback press.
Note: France, Finland and Sweden, press
5
z #
Dial the external number and press.
Press
d
Replace the handset to finish the procedure.
When an external line becomes free, you will be called back (recall
ring signal). You have to answer within eight seconds, otherwise
the Callback service is cancelled. While waiting for the Callback,
you can make and receive calls as usual. u
Lift the handset when you are called back.
The system calls the external number.
Note: Only one Callback can be activated on a busy
external line.
Cancel any single Callback #37* z #
Dial, enter the extension number and press.
Note: To cancel a single Callback on a specific external
line, dial the digit or digits to get a line instead of the
extension number.