Panasonic KX-TDE600 IP Business Phone System, Converged IP-PBX System expandable up to 1152 Extensions and 640 COs.Max CO Lines (640)Max Analog CO's (640)Max VoIP (H.323) trunks (32)Max VoIP (SIP) trunks (32)Max Total Extensions 992 (1152 with DXDP)**Even when Digital XDP is used, each shelf support..