The FXS/FXO is not important for the device when used as a repeater controller.
The Digium Interface is. In order to be used as a repeater controller a CM119 chip must be interfaced to the machine.
The Digium Interface allows me to make a daughter board that contains the CM119 and interface to the machine bus and a external interface.
Currently I use a thin client and a sound card board that i modify like this..