When another user does not answer your call to their internal extension because they are busy on a call, you can set a ringback. Once set, when the user ends that call, the system will ring you if you are free. When you answer the ringback call, the system then automatically rings the user. Note that a ringback set from the portal is separate from any callback set from your telephone.
If another internal user's status is shown as 
Busy - On Call, you can set a ringback on them. The system will then ring you when they end their current call and you are free.
To set a ringback:
1.Using the 
Directory gadget on the Main tab, locate the name that you require in the directory.
2.To filter the names shown, start entering a name or number in the text box at the top of the tab. As you enter a name, directory contacts that do not match are hidden from the view.
3. Hover your cursor over the busy contact. Click on the 
icon to set a ringback on that user.
4.The system will inform you that the ringback is set or if you already have a ringback set on another target.
To clear a ringback:
1.Repeat the process above to remove a previously set ringback.