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How does a closed circuit TV system work?
 

In case you have decided to buy a closed circuit TV system, there are a few things to think about concerning the complexity of the desired system. The following information will help you understand the basic elements of a closed circuit TV system.

 

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Here are some situations where a CCTV system can be used. 

 

Schools/ High schools

Many of today’s schools face security concerning problems.

How to protect pupils, staff and school premises from non-authorized intruders during school hours? How to protect school property at night and during the long school holidays?

During school hours the answer could be an access control system. The external doors of the building are automatically locked during class hours, and can be only opened using an authorized card in the system.

For external use video cameras can be used being linked to recording and monitoring equipments where there are many options available depending on the size of the project.

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Stores

The main concern in a store is how to prevent theft through shoplifting, when the supervising staff is limited.

In these cases a video camera can be placed where visual access is hard to get.

Apart all these, the use of a multiplexer unit to which a monitor is added allows viewing and recording of several cameras on a time-lapse video recorder, providing a very cost-effective solution to the problem.

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Remote Sites & Car Parks

Car parks and remote areas face the problem of having to watch over large areas while being able to transmit clear images back to the monitoring center.

Installing high-resolution cameras mounted high on towers on a pan and tilt mechanism and using remote monitoring can achieve this.

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Medium Retail Premises

Places such as high profile stores and the combined supermarket and gas stations face a constant battle against shrinkage. Goods strong visual evidence has become an important issue in ensuring a client successful conviction.

The use of electronic article surveillance (tagging) equipment linked to high-resolution cameras provides an ideal solution. Should an article be taken through the exit, an alarm would be raised and cameras triggered into operation.

 

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A CCTV system must consist of several video cameras for taking images, an image processor device, a monitor for visualization and a video recorder for image recording.

According to each objective specific requirement, different components can be added to the basic system. Thus the TV system is extended, new functions are added, getting to have a complex configuration after all. Additionally, the TV system may be linked to a burglary alarm system or to access control equipments.

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Video camera

Image taking device

 

Video cameras are placed in different points of the objective in order to take images of the watched area.

They can be monochrome or colored, fixed or pan and tilting.

Video cameras can be normal shaped, dome, picture hidden like, movement or fire detecting.

Cameras’ performances depend on several factors among which: sensitivity, resolution, lens type, etc.

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Image processing devices allow image recording and displaying in various formats.

The sequential switch allows image sequential preview. The time lapse within sequential commutation takes place is programmable. Should one image taken over from a certain camera be of some interest, the sequential switch would not move from that camera stopping commutation.

Multiplexers are especially used for grand systems where a total control of camera places is required. Irrespective of the sequential switch the multiplexer allows camera recording on a video recorder at a higher frequency. Each camera image will be continuously recorded being visualized later on a monitor by playback on the video recorder.

 

Multiplexer / Sequential switch

Image processing device

 

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Monitor

Image visualizing device

 

Monitors are devices used for displaying images taken over by video cameras.

According to the processing device, an image can occupy the whole screen or it can be divided to 4, 9, 16, etc., so several images could be simultaneously displayed.

Monitors can be monochrome or colored.

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They allow recording images taken over by cameras over a 3 up to 960-hour lapse on a 3-hour videotape.

They also allow a frame-by-frame image previewing in order to exclude any suspicion regarding happenings in a certain situation.

If they are provided with an alarm input, this input can determine recording initialization in case of event occurrence over a programmable time lapse.

An additional advantage is that a video recorder continuously displays on screen the time and date when recorded events occurred.

 

Time-lapse video-recorder

Recording device

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