In a DVR the analog video signal from an analog camera is encoded and compressed by the hardware inside the recorder.
In a NVR the analog video signal is encoded and compressed by a device connected to the TCP/IP network, the resulting IP video stream is transmitted over the network to the NVR for recording to the NVR Hard drives.
In the case of Patronus Labs all of the products except the NVR servers are sources of IP video. This enables the configurtion of very dynamic solutions. IP video stream can be transmitted over LAN, WAN, MAN, Wireless IP networks, or the internet from around the world and recorded in the NVR.