AASTRA 4223 Professional for BusinessPhone User Guide - Manual (Page 20)

Incoming Calls
BusinessPhone — Dialog 4223 Professional / Dialog 3213 20
Silent Ringing
This function is useful if you do not want to be disturbed by the
ringing of the telephone. Incoming calls will only be indicated on the
display and by the flashing Line key.
Note: For the Dialog 3213 this function requires the release
number R9B or higher, see the underside of your telephone.
In idle mode: É
Press to mute the ringer for incoming calls.
Save and redial incoming calls
When you receive an incoming external call, you can save the
number in order to redial it easily (the number can contain 24 digits
maximum). Previously saved number is erased.
Save number
Before you quit the call:
save
Press (see display).
Redial number
redial
Press to redial the saved number (see display).