Panasonic KX-TDA50G Digital Business Phone Systems, expandable up to 56 extensions and 12 COs. Max Ports up to 28 portsMax CO Lines 12Max Analog CO's 12Max VoIP (H.323) trunks 4Max VoIP (SIP) trunks up to 8 (with expansion card)Max Total Extensions up to 24 (48 with DXDP)Max Analog Propr..