What is it?
Video Surveillance or Closed-circuit television (CCTV) is a system of cameras, viewing monitors, and recording devices. Video cameras are usually permanently installed and designated to guard a particular area. These systems can be used in real-time to monitor activity or more commonly to investigate incidents after the fact by reviewing recorded images.
How Does it Work?
Analog: The most basic difference between analog and IP camera technology is the type of cable used to transmit signals. Each analog camera requires a coaxial and dedicated power cord. An analog camera signal can be transmitted over unshielded twisted pair (UTP) cable however it requires the use of specialized devices to keep the video balanced.
IP: Internet protocol (IP) cameras communicate over Ethernet cable. These next generation cameras can provide far better images than the traditional analogs. In most installations, IP cameras can use one Ethernet cable for both signal and power. The overwhelming majority of new CCTV camera technology developed today is IP.
Devices & Functions
- Box Cameras
Box cameras look like a box or rectangle. Most of these style cameras allow for quick and easy lens replacement. They can be used indoors just about anywhere with a wall or ceiling mount, but they are very susceptible to theft or vandalism unless they are placed in a protective housing.
- Dome Cameras
Dome or bubble shaped cameras are self-contained units. The camera, lens, and housing are all built together into one device. The exterior housing/dome can be hardened and installed with specialized screws to make it theft and vandal resistant.
- Bullet Cameras
Bullet or “lipstick” cameras are named for their shape. They are long and skinny with a built-in mount that makes for quick and easy installation.
Fixed lenses are efficient and inexpensive. However, since they can not be adjusted the only way to get a different view from a camera with a fixed lens is to relocate it physically.
A variable focal length or varifocal lenses provide a range of views from a single source. Lens focal lengths are measured in millimeters. A standard varifocal lens will provide for a range of views between 2.8mm to 12mm. With a varifocal lens, you can install the camera in an ideal spot and not worry about the exact view of the area. Once installed you can fine tune the picture by adjusting the lens.
Also known as a “zoom” lens, telephoto lenses are ideal for zooming into small areas over long distances.
- Pan-Tilt-Zoom (PTZ) Cameras
PTZ’s provide users with the ability to point the camera just about anywhere and zoom-in to get the best views. They can be programmed to run a pattern and scan a pre-defined area. PTZ’s work best when a live operator is using them for an active investigation. When set on a pattern and left unattended they often only catch part of an incident.
Selecting the right power supply is critical. Without enough power, the camera will not operate, and too much will damage it right out of the box. CCTV cameras operate on 12VDC or 24VAC. In any case, you need a power supply to step down the 120VAC provided by a typical power outlet or circuit.
Plug-in or wall transformers are quick and easy. They plug into a wall outlet and deliver a particular power solution through terminal leads. These power supplies can found in just about any voltage/amperage configuration needed.
Multi-port are the most common type of CCTV power supplies. They are given 120VAC power and convert it to multiple outputs for a group of cameras. The number of outputs is offered in multiples of four (4, 8, 16). Newer models will have space for backup batteries, so the cameras will continue to operate for a while during blackouts.
- Power-over-Ethernet (PoE)
PoE is a way to deliver power to a camera over the same cable that is used for video. IP cameras wire back to a switch that can provide PoE power to the camera while receiving the video signal for viewing and recording. When the switch does not have PoE capabilities or enough power capacity a Midspan or PoE injector can be used.
Video Management Hardware
- Digital Video Recorder (DVR)
DVR’s are just computers designed to record analog CCTV video. It has all of the main parts and pieces of a PC (motherboard, hard drive, operating system, power supply). Analog cameras plug into a dedicated port on the back of the DVR. The number of camera ports are commonly offered in multiples of eight (8, 16, 32).
- Network Video Recorder (NVR)
An NVR is the new DVR. The big difference is that NVR’s do not have hardwired analog camera ports. Network video recorders are purpose specific PC’s designed to record IP video. The NVR is connected to a network like any other PC and IP cameras are set to send video to the NVR’s hard drive. The physical connection of the NVR and IP camera to the network made is at the switch.
- Hybrid-Network Video Recorder (HNVR)
HNVR’s bridge the technology gap and help transition from analog to IP video. They have a number of hardwired analog ports like a DVR but also allow for network and IP camera connection as an NVR.
- Network Switch
The switch or switching hub is simply a computing device that connects many devices together to form a network. Some switches have the ability to provide Power-over-Ethernet (PoE) to cameras.
Video encoders make it possible to put analog cameras on an IP video network. The coaxial cable is removed from the DVR and connected to the encoder. The encoder connects to the network like any IP camera and the analog video is converted to IP.
Video Management Software (VMS)
Most CCTV technology manufacturers have developed their own versions Video Management Software. Essential VMS functions allow users to view live and recorded video, export video, control cameras, and set patterns. With the rise of IP video, many companies have created mobile app extensions of their VMS for iOS and Android. The big CCTV providers will let you download and install their software for free to try it out on a few cameras. You install it on your PC or server and program the cameras yourself. If you like it and decide to keep it, camera licensing can be purchased and installed to extend the software functionality beyond the free version.
Video Analytics can help solve very difficult problems with technology like facial recognition, license plate recognition, motion detection, object tracking, and may other applications. These extended functionalities are offered as software upgrades, licensed add-ons, or camera features.