The Analog CCTV camera
This is the type most répendu cameras today in the world of video surveillance, despite the arrival a few years ago IP cameras (more powerful and connected), the known analog keep its leading position CCTV thanks to some advantages: ease of installation, price and competitiveness are its major asset.
The operating principle is simple. The camera works in conjunction with a DVR (Digital Video Recorder) or HVR (Hybrid Video Recorder) that compresses and stores the video streams received from the camera.
The video is then visible on a screen either in real time or delayed by recording images.
This principle draws its ease, however at the time of the Internet at very high speeds and smartphones, it would be handy to be able to view distances supervised areas. An analog system allows this practice, but installation is complicated.
What is an analog signal
The BESTITUDE calls it as CCTV (Closed Circuit Television) this type of CCTV camera system uses analog NTCS to transmit the video stream. It was majority transmission system a few years ago, it was the protocol used by television channels to transmit their broadcasts. Today is a digital system that was chosen, the latter offering more opportunity.
An analog signal contains all information necessary to display an image on the screen:
- The synchronization “line” and “frame”
- The luminance information
- Color information
The information to be transported (from the camera recorder), they can not be sent all at the same time.The transmitted image is analyzed pixel by pixel sequentially from left to right and from top to bottom, so that at a time T, the video signal only contains information relating to a pixel.
The image is analyzed by line by line CCTV camera. The number of lines depends on the camera’s performance. Some may divide an image 400 lines while others go up to 1000 lines and more.
The camera first analyzes the even lines and odd
The set of even lines is called the even field and the set of odd lines is the odd field.
A video signal is thus composed of two frames.
A standard CCTV camera analyzes an image in 40ms, which corresponds to 25 frames / sec. This little value still change depending on camera performance.
Connectors and cables
Analog CCTV cameras are fitted with an output BNC for transmitting the video stream (and audio if the camera is equipped with a microphone). They all need connected to a recorder that can store the camera images.
The cable used is a coaxial cable. It has the advantage of being screened and therefore insensitive to External disturbance. It does not emits from either disruption.
To see: The Cable Guide
Advantages and disadvantages
|faithful replication signal||difficult signal processing|
|low Costs||complex storage|
|known and mastered technology|
What forms for Analog Camera
The analog CCTV camera comes in many forms, but for whatever its appearance, it retains all its qualities.
The choice of the shape of the camera is a criterion to be taken into account when buying a CCTV system.Indeed, depending on the installation area and the real purpose of the camera, some forms are more appropriate than others.
For example, a mini-dome camera , small and unobtrusive background particularly well in an interior space, its presence will be used primarily to confirm the identity of the person in case of offense.
In contrast, a box camera , rectangular like most seen in cities has a much more aggressive design and will also play a preventive and deterrent role outdoors.
– The IP cameras Guide
– The HD-CVI cameras Guide
Summary of CCTV technology
(With a fixed 3.6mm lens)
|Analog||· 700 lines: 2 meters
· 800 lines: 2 to 3 meters
· 1000 lines: 2 to 5 meters
|IP||· MP 1: 5 to 10 meters
· 1.3 Megapixel: 5 to 10 meters
· 2 Mpx: 10 through 15 mistresses
· 3 megapixels: 15 to 2 meters
|Wireless||· 800 lines: 2 to 3 meters|