You can activate the Service Observe feature to observe a call to an IP Phone, agent, or a Vector Directory Number (VDN). The phone displays the observing modes depending on the configuration made by your administrator.
Procedure
Press Main menu and scroll to Features.
Press Select.
Scroll down to Service Observe.
Press Select.
Select one the following options:
Basic
No-Talk
Next Call
By-Location
Enter the extension of the phone or agent or the VDN that you want to observe and press Enter.