Panasonic KX-TDE600 IP PBX System, expandable up to 1152 Extensions and 640 COs KX-TDE600's modular design lets you expand the system as your needs evolve. The Basic Shelf provides a maximum of 160 ports (288 ports with Digital eXtra Device Port [DXDP]). Plus with the KXTDE600's free slot architecture, you can easily insert expansion cards and access new features as well as expand your capabilities. This expandability means you can enhance system capabilities and features to meet your changing needs, without having to purchase a new system