“Close Circuit Television, Applications And Technology”
Closed Circuit Television (CCTV):- It is the television transmitted to a particular audience at specific locations Via coaxial cables, telephone wires, fiber-optics strands microwave radio systems, or communication satellites, as compared to open-circuit (broadcast) television intended for the general public. The usual closed circuit television picture display device is a television receiver. Most receivers use a cathode-ray tube to produce the visible image, although other devices such as flat-visible panel displays have become common.
Applications of CCTV :- Closed circuit television applications include (a) information display, (b) remote monitoring, (c)instruction cable television programming and (e)teleconferences and special events.
(a) Information display : Flight times in airports are displayed by closed-circuit television, typically on large cathode-ray tube video screens. A video screen may be used to display an image of the sales floor to a cashier at the front of a store, this setup is frequently installed for security reasons. In both examples, closed circuit television provides information but different methods are used for generating the video. The airport display usually shows text produced by a computer. The store screen shows the image of the sale floor produced by a video camera. These applications exemplify simple forms of closed circuit television used to connect a source of information to a restricted group of viewing locations.
(b) Remote monitoring: Many types of closed circuit television system produced pictures intended for distant viewing.These images may include those taken from a space probe passing close to a distant planet, or pictures of blast furnaces or other industrial operations that could be hazardous to human observers. At the opposite extreme the low cost of modern video equipment make practical the use of small camera to observe sleeping children at home and to enjoy video images of people faraway while chatting with them on the internet parking lots at shopping centers, store cashier location, bank and hotel lobbies, and other public places are often equipped with closed circuit television surveillance cameras and displays. These systems may be designed to function in nearly total darkness to delect suspicious activities or in brilliant surroundings to watch for hot spots in factory processes. Medical and scientific equipment and industrial robots often incorporate specialized closed-circuit television systems. Modern closed circuit television cameras used for remote monitoring are sensitive, rugged, relatively inexpensive, and durable with long service lives. Most modern solid state designs use charge-coupled imaging devices. Video signals are often recorded on magnetic tap for future use.
Instruction : Closed-circuit television has been available for many years for educational uses. Many universities and school systems employ television for teaching. Classrooms may be equipped with closed-circuit television cameras, recorders and receivers. Lesson material is often presented via video tape recordings, CD-ROMs, or DVD recordings. In other cases, classroom receivers are supplied with signals from specially reserved broadcast channels, cable television channels, or satellite channels. Audio circuits installed at viewing location sometimes allow two-way conversations between lecturer and students.
Cable television : Cable television was originally developed to improve broadcast reception in difficult receiving situations - for example, to bring distant signals from broadcast television stations to residents of ,mountain valleys or to serve viewers in cities where large buildings prevent satisfactory reception broadcast signals. Contemporary cable systems continue to distribute signal from local and distant television stations, but they now offer additional television services not available from broadcast stations, such as satellite-distributed news, music, movies, weather information, and locally originated community based programming wider availability has reduced the cost of using fiber-optic strands for high speed signal transmission. High speed interconnection enables closed-circuit television system to utilize important new kinds of digitally based services. For example, many telephone and cable television companies provide fiber-optic connections to schools and classrooms. These permit relatively inexpensive two-way video and audio systems, enabling great flexibility in system design and utilization.
Teleconferences and special events: Closed circuit television is used to conduct conferences among geographically separated groups of people. Signals from television equipped meeting rooms or studios are distributed by fiber-optical circuits, communications satellites, or the internet to connection centers, school or college or university classrooms, motels,hotels, or corporate locations. Two-way audio is typically provided, and conferences may involve many hundreds or thousands of people. Sports or musical events may also be televised and distributed in this fashion for viewing in suitably equipped theatres or auditoriums.
Closed-Circuit Television (CCTV) Technology: Closed circuit television systems frequently utilize equipment that produces signals based on broadcasting industry specifications. However, in contrast to the many possible design for closed circuit television systems, broadcast television is always limited to the use of standardized signals for its transmissions. The standardized television broadcast system used at present in the United States, Canada, Mexico, Japan and some other countries was devised in the 1950s by the National Television System Committee (NTSC). National television system committee systems display 30 complete television pictures (frames) per second, and each frame is composed of 525 horizontal scanning lines arranged from top to bottom.
Video cameras, television receivers, video cassette recorders (VCRs), and accessories are produced in large quantities for NTSC broadcast applications. The NTSC system is well suited for home entertainment, but its signal structure is technically limited by the requirement for simple, inexpensive home receivers and video tape recorders. Inauguration of improved kinds of advanced television system, most of them digital, is under way in many countries. Such technologies will eventually permit higher picture quality and the mass production of affordable receivers with new features. These features will eventually also become available for closed - circuit applications.
Special requirements: Closed-circuit TV (CCTV) systems are not required to use national television systems committee (NTSC) signals, but many do mainly for economic reason. In many applications, normal NTSC based closed-circuit television equipment is satisfactory. If the transmission path to the viewer is of low quality, special steps must be taken. In such cases, the signal can be modified to meet more closely the characteristics of the transmission system. For example, channel bandwidth can be reduced without loss of image resolution if the user accepts reduced quality in the representation of image motion. In that case, a rate lower than the normal 30 frames per second can be chosen. This is called slow scan closed-circuit television. Still frame video images sometimes suffice. A high quality still frame can be transmitted with picture elements being stored for seconds or even minutes in a memory system and then assembled for display after receipt of all data. This allows use of transmission channels having limited bandwidth. Most video pictures from space are transmitted at low frame rates over narrow bandwidth communication channels, and complete reception requires several seconds. Narrow band channels are also found on the internet, where both slow scan and still images are often used.
National Television System Committee (NTSC)broadcast signal characteristics may also be poorly suited to other kinds of specialized closed-circuit television applications. Some applications require high image resolution, great sensitivity to light, the ability to respond to infrared or ultraviolet light, or very rugged system components. Closed-circuit television requirements for high resolution display can be satisfied by increasing the number of image scanning lines and the overall video channel bandwidth. Industrial standards exist for high resolution closed-circuit systems. Cameras and monitors are available to meet other specialized requirements.
Advanced Development: The digital resolution has affected the design of all kinds of TV equipment. Video signal can be converted into digital form and processed by specialized computers, called digital signal processors. Visual special effects are often seen on entertainment television, including slow motion,still frames, rotation, inversions, and picture shape changes. They are accomplished by use of digital signal processing systems. In closed-circuit television (CCTV) applications, digital processing can make transmission via the internet practical and can also provide image enhancement. The excellent pictures from weather and surveillance satellite imaging systems are obtained with digital processing and enhancement. High performance solid-state camera sensors and the digital processing of video signals, taken together, have extended the applications of closed-circuit television systems. The advanced television systems now entering service make use of the advantage of digital signal processing to provide high quality images to the home, to the classrooms, and to industrial locations.
(The writer of this research paper is the eminent educationist, researcher, academician, and sociologist. He is the author of books like Advances and Development of science and Technology, Know your space and universe, Computer and the modern world, Television Transmitter and Receiver system, The threshold of education, Seasonal inputs and he can be reached at firstname.lastname@example.org)
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