Have you ever come across a Bogan Challenger Paging System? Well, I have. ONCE. Usually, people use Valcom for paging, but I came across one client that had an old Bogan system and wanted to integrate it with the CME for overhead paging. It turns out that the Bogan needs an FXO port to connect to. The customer would pick up the phone, dial "333", call get sent to the FXO port, to the Bogan, then out the speakers. Pretty simple. Here is what my dial-peer looks like in CME:
dial-peer voice 15 pots
description ===== Paging Overhead =========
destination-pattern 333 <----- dial "333"
port 0/1/0 <----- My FXO port
Now, the physical connection comes from my FXO port down to this thing called a 'Universal Telephone Paging Interface'. This thing has a port called a 'Trunk/Page Port'. That is where the FXO goes into. You see in the picture below the blue/blue-white pair. That goes to the FXO port. From there, on the right side, that goes into the back of the Bogan system, which has several knobs for volume, etc on the front. The back has the wiring, and I cant tell you how that thing is wired. It was already wired in the back, but I suppose the overhead speakers come into the back and the page is distributed through there.