A Trixbox server is installed, the extensions, trunk, inbound and outbound route are defined and working.
All extensions have a direct public number (no need for IVR or such for that).
The following additional funtions are needed:
*Direct call to extension: If call is not answered in X seconds, then also call the cell phone (and countinue to call on the extension)
*Call to main number:
-Call one extension in the group using Round Robin
-If the extension is not answered in X seconds, call all extensions defined in that group
In addition, a very short description of the steps needed to achieve this.