Cctv

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HISTORY

The first CCTV system was installed by Siemens AG at Test Stand VII in Peenemünde, Germany in 1942, for observing the launch of V-2 rockets. The noted German engineer Walter Bruch was responsible for the design and installation of the system.

In the U.S. the first commercial closed-circuit television system became available in 1949, called Vericon. Very little is known about Vericon except it was advertised as not requiring a government permit.

CCTV recording systems are still often used at modern launch sites to record the flight of the rockets, in order to find the possible causes of malfunctions, while larger rockets are often fitted with CCTV allowing pictures of stage separation to be transmitted back to earth by radio link.

The history of CCTV in the United States varies from that of the United Kingdom. One of its first appearances was in 1973 in Times Square in New York City. The NYPD installed it in order to deter crime that was occurring in the area however crime rates did not appear to drop much due to the cameras. Nevertheless, during the 1980s video surveillance began to spread across the country specifically targeting public areas. It was seen as a cheaper way to deter crime compared to increasing the size of the police departments. Some businesses as well, especially those that were prone to theft, began to use video surveillance. During the 1990s digital multiplexing, which allowed for several cameras at once to record, and introduced time lapse and motion only recording, increased the use of CCTV across the country.  This would have been preferable to the old style of camera due to the amount of time and money that could be saved. From the mid 1990s on, police departments across the country installed an increasing number of cameras in various public spaces including housing projects, schools and public parks departments. Following the attacks on September 11, the use of video surveillance has become a common occurrence in the country to deter future terrorist attacks.

In September 1968, Olean, New York was the first city in the United States to install video cameras along its main business street in an effort to fight crime. The use of CCTV later on became very common in banks and stores to discourage theft, by recording evidence of criminal activity. Their use further popularised the concept. The first place to use CCTV in the United Kingdom was King's Lynn, Norfolk. In recent decades, especially with general crime fears growing in the 1990s and 2000s, public space use of surveillance cameras has taken off, especially in some countries such as the United Kingdom.

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Picture : All CCTV

E4121 - Audio Visual System POLITEKNIK SULTAN SALAHUDDIN ABDUL AZIZ SHAH

INTRODUCTION

Closed-circuit television (CCTV) is the use of video cameras to transmit a signal to a specific place, on a limited set of monitors. It differs from broadcast television in that the signal is not openly transmitted, though it may employ point to point (P2P), point to multipoint, or mesh wireless links. Though almost all video cameras fit this definition, the term is most often applied to those used for surveillance in areas that may need monitoring such as banks, casinos, airports, military installations, and convenience stores. Video telephony is seldom called "CCTV" but the use of video in distance education, where it is an important tool, is often so called.

In industrial plants, CCTV equipment may be used to observe parts of a process from a central control room, for example when the environment is not suitable for humans. CCTV systems may operate continuously or only as required to monitor a particular event. A more advanced form of CCTV, utilizing Digital Video Recorders (DVRs), provides recording for possibly many years, with a variety of quality and performance options and extra features (such as motion-detection and email alerts). More recently, decentralized IP-based CCTV cameras, some equipped with megapixel sensors, support recording directly to network-attached storage devices, or internal flash for completely stand-alone operation.

Surveillance of the public using CCTV is particularly common in many areas around the world including the United Kingdom, where there are reportedly more cameras per person than in any other country in the world. There and elsewhere, its increasing use has triggered a debate about security versus privacy.

As the name implies, Closed Circuit Television (CCTV) is a system in which the circuit is closed and all the elements are directly connected. This is unlike broadcast television where any receiver that is correctly tuned can pick up the signal from the airwaves. Directly connected in this context includes systems linked by microwave, infrared beams, etc. This article introduces the main components that can go to make up CCTV systems of varying complexity.

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THE APPLICATIONS FOR CCTV

Probably the most widely known use of CCTV is in security systems and such applications as retail shops, banks, government establishments, etc. The true scope for applications is almost unlimited. Some examples are listed below.

Monitoring traffic on a bridge. Recording the inside of a baking oven to find the cause of problems. A temporary system to carry out a traffic survey in a town centre. Time lapse recording for the animation of plasticine puppets. Used by the stage manager of a show to see obscured parts of a set. The well-publicised use at football stadiums. Hidden in buses to control vandalism. Recording the birth of a gorilla at a zoo. Making a wildlife program using a large model helicopter. Reproducing the infrared vision of a goldfish! Aerial photography from a hot air balloon. Production control in a factory. The list is almost endless and only limited by the imagination.

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INFORMATION

1 - The Camera

The starting point for any CCTV system must be the camera. The camera creates the picture that will be transmitted to the control position. Apart from special designs CCTV cameras are not fitted with a lens. The lens must be provided separately and screwed onto the front of the camera. There is a standard screw thread for CCTV cameras, although there are different types of lens mounts.

Diagram 1 Camera And Lens

Not all lenses have focus and iris adjustment. Most have iris adjustment. Some very wide angle lenses do not have a focus ring. The 'BNC' plug is for connecting the coaxial video cable. Line powered cameras do not have the mains cable. Power is provided via the coaxial cable.

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2 - The Monitor

The picture created by the camera needs to be reproduced at the control position. A CCTV monitor is virtually the same as a television receiver except that it does not have the tuning circuits.

Diagram 2 CCTV Monitor

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3 - Simple CCTV Systems

The simplest system is a camera connected directly to a monitor by a coaxial cable with the power for the camera being provided from the monitor. This is known as a line powered camera. Diagram 3 shows such a system. Probably the earliest well-known version of this was the Pye Observation System that popularised the concept of CCTV, mainly in retail establishments. It was an affordable, do-it-yourself, self-contained system.

Diagram 3 A Basic Line Powered CCTV System

The next development was to incorporate the outputs from four cameras into the monitor. These could be set to sequence automatically through the cameras or any camera could be held selectively. Diagram 4 shows a typical arrangement of such a system. There was even a microphone built into the camera to carry sound and a speaker in the monitor.

The speaker, of course, only put out the sound of the selected camera. There were however a few disadvantages with the system, although this is not to disparage it. The microphone, being in the camera, tended to pick up sound close to it and not at the area at which it was aimed. There was a noticeable, and sometimes annoying, pause between pictures when switching. This was because the camera was powered down when not selected and it took time for the tube to heat up again.

The system was, though, cheap to buy and simple to install. It came complete in a box with camera, 16mm lens, bracket, switching monitor and 12 metres of coaxial cable with fitted plugs. An outlet socket for a video recorder was provided, although reviewing could be a little tedious when the cameras had been set to sequence.

There are now many systems of line powered cameras on the market that are more sophisticated than this basic system. Most of the drawbacks mentioned have been overcome.

Cameras had been around for a long time of course, before this development. The example is given to show the simplest, practical application. The use of some line powered cameras can impose limitations on system design. They do though, offer the advantage of ease of installation.

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Diagram 4 A Four-Camera Line Powered CCTV System

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4 - Mains Powered CCTV Systems

The basic CCTV installation is shown in diagram 5 where the camera is mains powered as is the monitor. A coaxial cable carries the video signal from the camera to the monitor. Although simple to install it should be born in mind that the installation must comply with the relevant regulations such as the Institute of Electrical Engineers latest edition. (Now incorporated into British Standard BS7671). Failure to do so could be dangerous and create problems with the validity of insurance.

This arrangement allows for a great deal more flexibility in designing complex systems. When more than one camera is required, then a video switcher must be included as shown in diagram 6. Using this switcher any camera may be selected to be held on the screen or it can be set to sequence in turn through all the cameras. Usually the time that each camera is shown may be adjusted by a control knob or by a screwdriver.

Diagram 5 A Basic Mains Powered CCTV System

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Diagram.6 A Four-Camera System With Video Switcher

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5 - Systems With Video Recording

The next development of a basic system is to add a video recorder, the arrangement would be as shown in diagram 7.

Diagram 7A Multi Camera System With Video Recorder

With this arrangement the pictures shown during play back will be according to the way in which the switcher was set up when recording. That is, if it was set to sequence then the same views will be displayed on the monitor. There is no control over what can be displayed.

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6 - Movable Cameras

So far all the cameras shown have been fixed with fixed focal length lenses. In many applications the area to be covered would need many fixed cameras. The solution to this is to use cameras fixed to a movable platform. This platform can then be controlled from a remote location. The platform may simply rotate in a horizontal plane and is generally known as a scanner. Alternatively the platform may be controllable in both horizontal and vertical planes and is generally known as a pan, tilt unit. A basic system is illustrated in diagram 8.

This chapter does not deal with how cameras are controlled or wired; it is just showing the facilities that may be incorporated into a CCTV system. Therefore the diagrams that follow are simply descriptive block diagrams and not connection drawings.

Diagram 8 Basic Movable Camera System

Cameras may be used indoors or outdoors. When used outdoors they will always require a protective housing. For indoor use the environment or aesthetic constraints will dictate whether a housing is needed. Systems may contain a combination of both fixed and movable cameras.

Diagram 9 Multiple Camera System

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CCTV SCHEME BLOCK DIAGRAM

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E4121 - Audio Visual System POLITEKNIK SULTAN SALAHUDDIN ABDUL AZIZ SHAH

E4121 - Audio Visual System POLITEKNIK SULTAN SALAHUDDIN ABDUL AZIZ SHAH

E4121 - Audio Visual System POLITEKNIK SULTAN SALAHUDDIN ABDUL AZIZ SHAH

E4121 - Audio Visual System POLITEKNIK SULTAN SALAHUDDIN ABDUL AZIZ SHAH