AASTRA DT590 for MX-ONE User Guide EN - Manual (Page 82)

Other Useful Features
DT590 82
Emergency mode
In the event of an emergency, the operator can set the exchange
into Emergency mode, during which only preprogrammed
extensions are permitted to make calls. If your extension is not
assigned with this category and you try to make a call, you will not
receive a dial tone.
Malicious Call Tracing
If you are disturbed by bothersome or malicious external incoming
calls, you can request number tracing from the network provider.
You can invoke tracing during or after an ongoing conversation.
The external line can be held for a limited period of time.
Order
During an ongoing conversation: »
Press.
Dial tone. *39#
Dial.
The system acknowledges with different tones whether the tracing
request was accepted or rejected.