CCTV Security Systems Chennai India
VIDEO SURVEILLANCE INFORMATION PORTAL FOR CCTV Closed circuit television (CCTV)
CCTV is a collection of video cameras used for video surveillance.
CCTV is generally used in areas where there is an increased need for security, such as banks, airports and town centres. CCTV was initially developed as a means to increase security for banks but over time it has developed into a cost effective means of general video surveillance and home security.
Camera, lens and power supply. Recording device, VCR or a digital video recorder. A monitor. Wiring
CCTV Cameras
The primary function of a cctv camera is to convert light into a video signal, all cctv cameras require an optical lens to focus the light onto an image sensor located directly behind the lens inside the cctv camera.
Different types of cctv cameras are Board Cameras,C Mount Cameras,IR Cameras,IP Cameras,Zoom Cameras,Speed Dome Cameras.
CCTV Lenses
It is also the job of the lens to control the depth of field of the image, either for a wide angle image or a narrow angle image depending on the distance of the object in question from the cctv camera. Where movable cctv cameras are used a zoom lens is usually fitted to allow varying points of a monitored area to be viewed. Zoom lenses are usually controlled by the CCTV operator.
The recording device receives and stores the images from the cctv camera, previously time lapsed VCR’s and video multiplexers were generally used in CCTV systems, but due to developments in technology digital video recorders are now more commonly used.
Digital video recorders use computer hard drives to store the recorded information and can however record for much longer depending on the size of the hard drive and the CODEC being used. A DVR combines and enhances the recording capabilities of a time lapse VCR and a multiplexer.
When there is a requirement for recording more than one cctv camera and video switcher can be used, the cameras are connected into the switcher and the switcher will automatically switch the image being fed to the monitor and the video. The disadvantage of using a switcher is that if there is an incident it is possible that the cctv camera image will change causing the incident to be missed.
A multiplexer is a device that takes multiple video images and lays them onto a VHS tape, it uses the properties of the PAL signal to record as many images from multiple cctv cameras every second as possible. The video information recorded is limited by the amount of cctv cameras on the system and the length of time the VCR is set to record for.
A stand alone DVR is designed specifically for CCTV systems. It uses computer hard drives to store video information and an embedded operating system to control the functions of the DVR, this type of recording device is most commonly used with current CCTV systems. CCTV Digital video recorders have various settings to enable more video information to be recorded at the required times using technology such as video motion detection, this means that the images from the cctv cameras are only recorded when the information of the image changes, for example a person walking in front of the cctv camera.
Many DVRs can also be connected to a network or a modem to allow remote access.
CCTV PC based digital recorder
CCTV Network video server
CCTV Monitor
There are advantages and disadvantages for both monitors, A TFT monitor is less space consuming than a CRT monitor. A CRT monitor will display a better image of low and medium resolution cameras than a TFT monitor. For high resolution cameras, a TFT monitor can be more cost effective than using a high resolution CRT monitor.
Developed in the late 1940’s as a miniature version of the Type C connector, Bayonet Neil-Concelman (sometimes erroneously called a British Naval Connector or Bayonet Nut Connector). A connector widely used in the CCTV industry, usually for coaxial cable. Easy to install and reliable with little video signal loss. A rotating ring outside the tube locks the cable to any female connector.
All cctv cameras require a degree of lighting to be able to pick up an image, monochrome cameras generally work well in darker environments than colour cctv cameras. Infrared lighting can also be used with monochrome cctv cameras.
Infra red lighting can illuminate areas at different frequencies, although invisible to the naked eye, CCTV cameras can see the light emitted. Depending on the frequency range that the IR lamp operates, depends on how visible the lamp glow is to the naked eye. Note however, not all cameras are sensitive enough to pick up all frequencies of infra red.
Covert CCTV is the practice of using video cameras in locations that are not made obvious to the persons being monitored in the specific cctv camera coverage area, but it is recommended that there is reasonable cause for the purpose of covert surveillance and that its primary objectives are clearly noted, only used for the purposes of preventing crime and are not used for longer than intended.
Remote CCTV is the means of accessing CCTV images over a computer network or standard telephone networks. Software is used on the local PC that allows access to the digital video recorder.
IP CCTV refers to Internet Protocol Closed Circuit Television; traditional CCTV systems use digital or analogue cameras using analogue cables that connect to a recording device such as a digital video recorder. IP cctv cameras are designed to plug onto any existing wired or wireless computer TCP/IP network, or directly onto a broadband connection so that the cctv camera can be accessed by any computer connected to the network, this includes over the internet.
CCTV Video Signal
CCTV Video Transmission
The most commonly used cable for wired transmission is RG6 coaxial cable.
Other forms of video transmission include fibre optic cables, microwave transmission and licence free radio transmission.
Resolution refers to the number of definable parts of the horizontal image produced by a camera, recorded by the video or digital video recorder and displayed on the monitor.
The TVL of the analogue PAL video information is closely compared to the pixels of a digital image.
The recording device should be the deciding factor when choosing the resolution of a camera as a 520 TVL camera being recorded on a VHS recorder will only record 240 lines out of the available 520 lines.
CCTV Codec’s
There are many standards of CODEC, those used for video compression that you may come across are MPEG-2, MPEG-4, JPEG 2000, AVI and H.264, H.264 is the latest codec being introduced into the CCTV market, deriving from video conferencing equipment.