CCTV video surveillance systems have existed for over 25 years, starting out as completely analog systems that have gradually become digitized. Today's CCTV surveillance systems have come a long way from early analog tube cameras connected to a VCR. CCTV surveillance systems now exist primarily in two forms: a traditional analog system with a network DVR, and a network video system using network cameras.

Traditional Analog CCTV Surveillance System with a Network DVR
An analog CCTV system using a DVR (Digital Video Recorder) is an analog system with digital recording. In a DVR, the videotape is replaced with hard drives for video recording, which requires video to be digitized and compressed in order to store as many day's worth of video as possible. With early DVRs, hard disk space was limited, so recording duration also was limited or intentionally degraded to allow for more space. With the constant advancement of computer technology, space is really no longer a major concern. Most DVRs have several video inputs, typically 4,9, or 16, which means they also include the functionality of traditional quads and multiplexers. What really makes this type of system so useful and flexible is the network connectivity of the DVR. An analog CCTV system using a network DVR is a partly digital system which includes a network DVR equipped with an Ethernet port for network connectivity. Since the video is digitized and compressed in the DVR, it can be transported over a computer network to be monitored on a PC in a remote location. Most systems can monitor both live and recorded video, allowing for real-time viewing of live and recorded video from multiple locations simultaneously. In addition to live and recorded viewing of video remotely, network DVRs allow for remote control of PTZ cameras and easy export of video clips and snapshots onto whatever computer is remotely connected.


Network Video CCTV Surveillance System with Network Cameras
A network camera combines a camera and computer in one unit, which includes the digitization and compression of the video, as well as a network connector. The video is transported over an IP-based network, via network switches, and recorded to a standard PC with video management software. This represents a true network video system, and is also a fully digital system, where no analog components are used. A network vidoe system using network cameras allows for high resolution cameras (megapixel cameras), consistent image quality, Power over Ethernet (POE) and wireless functionality, digital inputs and outputs over IP in addition to video/audio, and easy flexibility and scalability.