AASTRA 4187 Plus for BusinessPhone User Guide EN - Manual (Page 22)

Outgoing Calls
BusinessPhone – Dialog 4187 Plus 22
Automatic Callback
You call an extension and receive busy tone or get no answer.
Automatic Callback can also be used if no external line is free. 5
Press.
Verification tone.
Note: The number for Automatic Callback may differ from
country to country, see table “ Alternative Programming for
Camp-on, Automatic Callback, Call Pick-up, Intrusion ” on
page 69. d
Replace the handset.
You are called back if the extension finishes the ongoing call or the
next time the extension finishes a new call. You have to answer
within eight seconds, otherwise the Callback service is cancelled. u
Lift the handset when you are called back.
The requested extension is called automatically.