Aastra SIP 53I Administrator's Manual page 167

Configuring Network and Session Initiation Protocol (SIP) Features
Network Settings
IP Phone UI
Step Action
8 Enter the IP Address (in dotted decimal) or qualified domain name for the Time Server.
9 Press Done to save the change.
Use the following procedure to enable/disable and configure the NTP Servers
using the Aastra Web UI.
Aastra Web UI
Step Action
1 Click on Advanced Settings->Network->Advanced Network Settings.
2 Enable the "NTP Time Servers" field by checking the check box.
(Disable this field by unchecking the box). Default is disabled.
41-001160-00, Release 2.1, Rev 04 4-43