I need to know can the Cisco Systems 804 ISDN Router work with a cable-modem connection? The technical specs for this router say that it has: 4 x 10BaseT Ethernet LAN (RJ-45 Connector), and 1 x ISDN BRI (Basic Rate Interface) S/T (RJ-45 Connector). I don't have an ISDN BRI. I have cable-modem (RJ-45 Connector). I need to know will it work before I buy the router.