Ibby
Your FXS(foreign exchange station)needs a FXO (foreign exchange office) is a service that can be ordered from the telephone company that provides local telephone service from a CO which is outside(foreign to) the subscribers exchange area.you need a (FX)foreign exchange trunk. Connecting POTS telephones to a computer telephone system via T-1 links requires a channel bank configured with FX type connections. your PBX needs FXO connection configured I hope this helps
Herschel