Video Cassette Recording (VCR)

Today, security camera system may consist of many different products and technologies. Many suppliers build pieces of the system, whether it is part of a hybrid analog/digital implementation or an end-to-end networked IP solution. The following sections explain the evolution of the CCTV system, starting with a fully analog system and adding components until it achieves networked capability.

A traditional analog surveillance system consists of analog cameras, time-lapse VCRs and monitors. A coaxial cable runs from each camera to a multiplexing device, which allows multiple cameras recording to one VCR, with a monitor for viewing. The time-lapse VCR allows the operator to adjust when the VCR records so the standard two-hour VHS tapes can he used for much longer. The trade-off results in lower-quality images in return for less frequent tape changes or image overwriting.

Analog CCTV recording systems have been the basis surveillance and monitoring for the past twenty years .This technology is extremely old and outdated and is rapidly being replaced by digital recording technology which now represents over 80% of all new installations.

Digital Video Recording (DVR)

A DVR is a computer with a special video graphics card that connects it to an analog camera via 75-ohm coaxial cable. The card also converts the analog signal to a digital signal and compresses the resulting image so it can be stored on an internal hard drive, viewed or transported across a network. DVRs typically utilize a computer operating system such as Windows or Linux along with video management System (VMS) software. DVRs are controlled and accessed via keyboards, mice and external monitors in order to setup, run surveillance software and replay stored video. DVRs usually have an internal Ethernet connection for LAN or WAN attachments.

Network-Attached Digital Video Recorder (NDVR)

A Network-attached Digital Video Recorder is part PC and part "Network Appliance" A NDVR is very similar to a DVR and is sometimes called a "Network Appliance" because it does not require-attached keyboard, mouse or video monitor. The device is plugged directly into an Ethernet switch and the only way to access the device is through the network. The device still has an operating system but it resides in firmware burned into a chip on the motherboard. Most of these NDVRs rely on Video Management Software (VMS) loaded on a network-attached client PC, however some have it 'embedded' in another motherboard chip, where it can be accessed from any PC through an Internet Browser. Most of these products have internal hard drives for local video file storage, but they can be inter-connected with Direct Attached Storage Arrays (DAS), Network Attached Storage (NAS) equipment or Storage Area Networks (SANs) through the LAN or WAN.

Network Video Recorders (NVR)

The 'pure' Network Video Recorder (NVR) is not a "turn-key box" or network appliance, but created with a combination of network devices. An NVR can be a standard network server with internal or attached storage capability along with recording software, video surveillance system or communication software and possibly even intelligent video analysis software. Digitization of the analog video is done by a separate 'Video Encoder' or 'Video Server' which is also attached to the Ethernet/IP network. Using an NVR configuration, true IP cameras can act as Video Servers and input images directly to the NVR and be managed directly by the NVR video software.

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