If a Emergency Center wants to configure a camera or DVR in another network, the router at the remote location has to make an IP Address translation (NAT) from the Emergency Center to the camera or DVR. Portforwarding also has to be set to redirect the TCP packets to the right location, in this case, a camera or DVR. 



For example:

The public IP address (Internet IP Address) of the remote location is 89.186.50.70 while in it’s private IP network it’s within the 192.168.2.* range. The camera or DVR has IP address 192.168.2.101 and can be reached by using port 80.



For an emergency center to be able to receive video, the router at the remote location has to be configured to redirect an incoming request for public IP 89.186.50.70:80 to local IP 192.168.2.101:80