no no no no
The X100 card is a rebadged voice modem. It can work decently well, but is often the cause of a wide range of issues. Worth a shot i suppose, but i would never use one in a situation where it failing will lose somebody money.
Being a rebadged voice modem, it has two ports just like any other modem. You plug your phone line into one. The other is the ‘phone’ port, so if you have a phone on your desk you can plug it there. It is disconnected when the modem is in use to prevent you from interrupting the data stream.
Being asterisk is not sending data, the 2nd port is useless. Ignore that it is there.
FXO is input, FXO connects to a phone LINE. FXS is output, it connects to a PHONE, and provides that phone(s) with dialtone, battery voltage, ringing when a call comes in, etc etc. If you forget this alot, just remember that FXS Serves.
The X100 or clones do NOT have an FXS port. They have ONE FXO port and one useless port.
What do you mean by ‘phone distribution system’? Is this a phone system? IE, in your current configuration can you call from one extension to another? Or if you are talking on the phone and pick up another phone, you hear the first call?
The ‘right’ way to do this is to install one FXO port per line you have, and one FXS port per phone you have. Then each port is assigned its own extension number so they can be dialed separately. You can also assign extensions to ring some or all of them. The advantage of this type of setup is that each phone will ALWAYS get a dialtone regardless of who else is on the phone. You can only have as many outgoing calls as you have FXO ports connected to lines, but the inside phones can always call each other.
If you are going to do something like this, how it would work depends on how many lines and phones you have. If you need 8 or less total ports (lines+phones), try a Digium TDM400 series card. They have 4 ports each and when you buy it you can select what modules (FXS or FXO) go in each port.
If you need more than 8 ports, try a Sangoma A200. Using the ‘remora’ modules, you can fit up to I think 20 ports per system.
You could also use ATAs. An ATA (analog telephony adapter) is a small device that connects to * via VoIP (over ethernet) and provides 1-2 FXS ports.
Lastly (best option IMHO) you can use IP phones. IP phones are phones that have Ethernet ports where the phone jack would be. They connect to * directly over VoIP (SIP protocol) and let you much more easily do things like hold/transfer/conference, as there are buttons to do it instead of star codes. Cheap IP phones can be had for as low as $50/each (Grandstream BT100 series). Many models are available based on your price range.
Hope this helps!