Analog CCTV application, security cameras capture an analog video signal and transfer that signal over coax cable to the Digital Video Recorder (DVR). Each camera may be powered by plugging in the power supply right at the camera or by using RG59 Siamese cable which bundles the video and the power cables.
The DVR converts the analog signal to digital, compresses it, and then stores it on a hard drive for later retrieval. Intelligence is built into the DVR to handle such things as scheduling, motion detection, and digital zoom. Monitors for viewing the video are connected to the DVR, or it can be set up to publish over an internal network for viewing on PCs.
The DVR can also be set up to broadcast over the Internet and can add password protection and other features. When broadcasting over the Internet, the video for all of the cameras is transmitted as one stream (one IP address). Therefore, it is very efficient.
In the IP world, each network camera captures an analog image but immediately converts it to digital inside the camera. Some digital processing can happen right at the camera, such as compression and motion detection. The digital video stream is then broadcast over the local area network (LAN) using Ethernet (CAT5 or CAT6) cable.
Power is supplied to the cameras through the ethernet cable via Power-Over-Ethernet (POE) adapters built into the cameras and at the (POE enabled) switch. (FYI - Older style IP cameras do not have POE built in so POE adaptors had be added to the system like this.) The ethernet cable for each camera is plugged into the switch which feeds into the network hub. As with all network devices, some set-up needs to be done for each network camera to set up its IP address and other identifying attributes.
A Network Video Recorder (NVR) performs the same function as its DVR cousin in the analog world. It captures each camera's signal, compresses, and records it. The main difference is that the video feeds are digital (and much higher resolution) and not analog. Software built into the NVR provides features such as intelligent search and zoom, etc. The NVR combines the video streams from the cameras and handles the broadcast over the LAN and internet for local and remote viewing.