Using a button programmed to the Ring Back When Free function
If the button has status indication, it will show that a ring back has been set. The button can also be pressed again to cancel the ringback.
Use a short code set to the Ring Back When Free function
A short code set to this function can be used to set a ringback on any extension without having to actually make a call.
IP Office Phone Manager
This application provides the user with a button to set a ringback.