Panasonic KX-NT IP telephones and the computer based IP Softphone are designed to ONLY work when connected to a Panasonic KX-TDA100/200/600 Hybrid IP-PBX system control utilizing a KX-TDA0470 16-channel IP Extensions Card. 

One of the benefits of using IP telephones in a managed IP network is the elimination of additional cabling by leveraging the existing data network. Another large benefit is that it allows remote office workers direct communication to the TDA system when installed over a managed IP VPN, requires high speed internet services (Cable/xDSL/Internet).

The number of IP telephones is based on which KX-TDA model you have and the number of 16-channel IP Extension cards it will support.