Closed circuit television, or CCTV, is used in different situations all over the world, and there is a good chance that most people have appeared on a CCTV network, whether they intended to or not. Most retail businesses employ a CCTV system to keep track of each customer that enters a store, deterring theft and vandalism.
Identification
A CCTV network can only be accessed by display units directly connected to the network. A CCTV network uses coaxial cable, infrared beams or microwaves to broadcast the signal to the connected receivers. This differs from a standard open television network in that anyone tuned to the open network's frequency can access the images being broadcast. With CCTV, the access is restricted.
Functions
CCTV has many practical applications, and it is in use in facilities and homes all over the world. A company may employ a CCTV network as a form of security to monitor the company grounds, and a private residence can employ a CCTV network in the same way. CCTV networks can be used in hospitals to allow nurses to keep an eye on multiple patients at the same time, and they can also be used to monitor traffic at busy intersections.
Features
The majority of the video cameras used in a CCTV network use cameras that have a charged coupled device (CCD) chip for capturing digital images. This device creates images using small charges of electricity that are emitted when light hits a pixel. Each CCD chip generates hundreds of thousands of pixels that make up the image.
Recording Device
Each CCTV network has a time-lapse recording device that captures the images and stores them for use at a later time. Many CCTV networks are beginning to implement digital archiving systems that store all of the images on a series of computer hard drives, but many existing CCTV networks use VHS tape as their method of recording. With CCTV time-lapse technology, it is possible to store 24 hours of surveillance on one tape.
Monitors/Displays
Monitoring CCTV cameras can be done in different ways. In some cases, a CCTV is meant for entertainment purposes, such as the presentation of a boxing match on a pay-per-view network, so these CCTV images are professionally edited for presentation. Most CCTV networks use switchers, quads or multiplexors to keep track of what each camera is capturing. A switcher displays the image from a camera for a few seconds and then automatically switches to the next camera. A quad system feeds images from up to four cameras into one display. The images of each camera in a quad system are recorded separately, but the quality is diminished because they only occupy one-fourth of the screen. A multiplexor is a high-speed switching device that can display and record the images of up to 16 cameras in full-screen mode and quality.
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