Aastra SIP 53I Administrator's Manual page 250

IP Phone Administrator Guide
Operational Features
Aastra Web UI
1 Click on Basic Settings->Preferences->General.
2 Enable the "Suppress DTMF Playback" field by checking the check box.
(Disable this field by unchecking the box). Default is disabled.
3 Click
You must restart your IP phone for the changes to take affect.
4 Click on Operation->Reset.
5 In the "Restart Phone" field click
5-40
to save your settings.
to restart the IP phone and apply the changes.
41-001160-00, Release 2.1, Rev 04