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As with everything, CCTV can be as simple or as complex as the occasion demands. The significant difference between CCTV and intruder or access control systems is that different degrees of skill, experience and training are required from designers and installation engineers. Another factor is that fault finding requires particular experience on the part of service engineers. This is not to denigrate the essential skills of alarm engineers, but it is a fact that their training is not directly transferable to the needs of CCTV installation or servicing in anything other than basic systems.

This article looks at the needs of the more complex industrial and commercial systems. There are, of course, plenty of do-it-yourself CCTV systems on the market that provide excellent quality and performance.

As with all debates there are two points of view, in this case the expectations of the customer and the capability of the installing company. Either can be very high or very low depending on their previous experience. Let two examples illustrate this from the author's direct experience. Neither problem needed any great knowledge of CCTV theory to resolve. Mainly the application of common sense and interpretation of manufacturer's specifications.

During a visit to a site demanding a very high level of security, the views on two CCTV monitors were noticed as being appalling, with almost no definition. This was not commented on at the time because the visit was for a totally different reason. Later, however, a comment was made and the customer stated that the installation was technically very difficult and the installing company had said that this was the best that could be achieved under the arduous conditions that prevailed at this site. Engineers had returned on many occasions and could not improve the picture quality. The expectation of this customer was, therefore, that with all the technical resources of this large installation company, he was obtaining the optimum performance. An inspection of the site was made and the conditions were indeed demanding. It was discovered that the cameras were up to one mile away from the control, and underground, the illumination being by means of infra red lights. The cameras were connected back to the control by a very large coaxial cable. Furthermore, at the control the video signal was fed to a video motion detection system, and then on to five separate monitors.

A series of tests was suggested to which the customer agreed. It was intended to replace the coaxial cable with a 'twisted pair' but site conditions precluded this possibility. A video launch amplifier, designed to send a video signal down a coaxial cable, was fitted at the camera end and a line corrector at the control end. This resulted in a dramatic improvement in picture quality and, for the first time, the video motion detection system worked correctly. An additional light was installed at the camera end to increase the levels and allow the lens to operate at a smaller aperture, which increased the depth of field. There were still problems with the remote monitors until it was discovered that they were all terminated at 75 ohms. Simply setting all except the last monitor to 'high z' cured this problem.

This was a classic example of a poorly designed and badly installed system. The tragedy was that the customer thought that it was the best that current technology could produce. He may well have been put off CCTV as a practicable proposition for future applications.

The second example was when I was asked to look at a system that had been designed by a salesperson, apparently based on a cursory knowledge obtained from a distributor's catalogue. The manufacturers of the installed equipment produce most impressive brochures and sets of data sheets, and the products are well regarded in the industry.

The system comprised four cameras around the outside of an industrial building, connected to a quad screen splitter and a time lapse video recorder. One of the cameras was also connected to a video motion detector covering the main entrance.

The customer's expectation of the system was that, if a vehicle entered the yard outside normal working hours, the system would go into alarm. The identity of the vehicle and any other activity around the building would be recorded. Here was the first flaw in communication; the customer's interpretation of 'identity of the vehicle' meant reading the number plate, but he also wanted to see the entrance and where the vehicle went.

There was not much of the system that functioned at all. The video motion detector was sometimes set off by passing traffic, sometimes not; sometimes by vehicles entering the yard, sometimes not. The front camera was fitted with a wide angle lens to view the whole yard and had absolutely no chance of reading number plates. In addition, it was mounted about two metres up a wall, facing east over open country.

The quad screen splitter was set to record a full picture on alarm, so the other cameras were not being recorded. Even if the splitter was not set in this mode and recorded in quad screen, the pictures would be too small to be of use.

The time lapse video recorder was set in 24 hour mode and switched to real time on alarm. The problem was that, with only a few incidents over- night, reviewing the tape was a tedious procedure (assuming the system had worked as intended).

In principle, the system seemed reasonable on paper and the customer would have no basis for doubting what was presented to him. However, the individual items were not correctly selected. The person who designed the system had obviously come across various pieces of equipment through exhibitions and advertising, but had no depth of understanding of the specifications or what questions to ask of the manufacturer. Also, it was apparent that the system had been designed down to a price under pressure from the customer. It is a sad indictment of parts of the industry that sales people try to find the cheapest solution rather than concentrate on finding the right solution. Even sadder is the probability that many do not have the training to know the right solution. The following changes were made to produce an acceptable working system.

The video motion detector initially installed was a type only designed for indoor use, or limited outdoor use in fairly constant lighting. (The price of under £200 should have indicated the limitations.) A phone call to the manufacturer confirmed this. The unit was replaced with a budget version of a more sophisticated video motion detector with a range of more sensitive set-up parameters. This functioned as expected.

The lens on the front camera was changed to one with a longer focal length so that it only viewed the area that would catch vehicle number plates. Also, it was moved higher up the wall and looked down at the area to avoid the problem of looking directly at the rising sun.

The camera viewing along the front of the building was swung around to view the general area of the entrance.

The quad screen splitter was replaced with a low cost multiplexer so that all cameras were continuously recorded when alarmed. This enabled any camera to be viewed individually in full screen, or all four at once for general analysis.

The time lapse video recorder was replaced with an event recorder that only recorded in real time when an alarm was active. This provided rapid reviewing of the previous night's, or even previous week's, events without the need to plough through hours of inactivity.

The result was a system that achieved the expectation of the customer, although at considerable unnecessary cost to the installer. The cost of the final equipment installed was not a great increase on the original and would certainly not have lost the company the contract.

Whilst there are companies that offer a competent and professional service, there are many more that do not have the depth of technical knowledge to design larger systems that produce acceptable results. In the case of CCTV in particular, there are many factors that must be taken into account in designing an effective system. In some instances there may be restrictions caused by the Laws of Physics of which the customer should be appraised. Some of these factors are listed below.

There is a limited depth of field in focus in low light conditions when the lens iris is fully open; it is also a function of the focal length and the object distance. The depth of field decreases when the 'f' number is smaller (the aperture is larger); the focal length is longer; the object distance is shorter.

· There is a shift in the area of view in focus between daylight and illumination by infra red light. It may be necessary to accept a compromise between day and night focus with a fixed focal length lens, or to decide which is the most important.

· The image should remain in focus throughout the range of a zoom lens. If the focus has to be adjusted every time the zoom is altered it indicates that the back (mechanical) focus adjustment of the camera is incorrect.

The limiting resolution of a system may be a video tape recorder. Irrespective of the quality of the cameras, this is generally from 240-400 TV lines for monochrome systems and 240-330 lines for colour.

· A type of video recorder known as S-VHS (super VHS) is available and often quoted as producing 500 lines resolution (for colour only). This is not always practical for use with industrial video systems because the input to the recorder must be made up of separate luminance and chrominance (Y/C) signals. Apart from the need to run two separate coaxial cables to every camera there are few switchers or multiplexers on the market to accommodate this type of input. Having said this there are new products appearing on the market that overcome this problem. As always, check carefully with the manufacturer before using them based on the advertising.

· Manufacturers' specifications for cameras can be very confusing to the uninformed. Many installers simply look at the factor called' sensitivity' expressed in Lux. It is necessary, however, to look further; is this at fl.2, fl.4? Is it at 79%, 100% reflectivity? Is it with AGC on or off? Is it with a 'gamma' of 1 or.45? Is it' usable' video or full video? Unless all these factors are taken into account, a true comparison of specifications cannot be made. There can be a three times difference between cameras of similar actual specification. Are you really getting what you are paying for? If in doubt seek professional advice.

In conclusion, therefore, these are just a few of the factors that must be taken into account when designing a CCTV system; it is not like a 'point and shoot' camcorder. It is important that the customer is made aware of the limitations as well as the advantages of the system being proposed. In particular, the view as seen on the monitor should be defined accurately or demonstrated. There is no lens in the world that can emulate the human eye, yet we all live every day with the most incredible and adaptable lens and tend to imagine that a modern camera can reproduce similar views. We see in three dimensions with continuously adjusting focus but a camera sees only a flat plane with restricted depth of field. The question of what the customer thought would be seen compared with the actual view obtained probably causes more debate and ill feeling than any other aspect of CCTV

The final selection of lens is frequently a compromise from the ideal and should be discussed with this in mind. In this way the expectations of the customer will always be achieved and a satisfied customer pays the bill.

This chapter is supplied by Mike Constant and was originally published in CCTV Today. Mike is the author of 'The Principles & Practice of CCTV' which is generally accepted as the benchmark for CCTV installation in the UK. Also produced by Mike is a CD-ROM titled: 'The Complete Handbook of CCTV' which is a self study course for those who wish to become proficient in CCTV design and installation. Again you can view this product and request a purchase by following the enclosed links.

For those specifying and designing CCTV systems, an indispensable tool is Lenscalc which enables the correct choice of lens for each application. Designed by Constant Consultants, you can try it out online

Our thanks and appreciation to Robyn Sones who allowed us to use this content.

Please visit their site www.cctv-information.co.uk at any time for additional information you might need..
 

Although the application of CCTV security have not changed very much over the past years, the tools and equipment have significantly. Cameras became smaller, cheaper and better, but the major breakthrough happened in recording equipment.

Therefore many customers shopping for complete CCTV monitoring and recording systems are confused by such a verity of available products. Goal of this article is to guide buyers toward best possible and most economical type of CCTV equipment, based on intended implementation and requirements. Selecting the right cameras.

It is virtually impossible to describe all types of available security cameras in this short article. We will focus our attention on most popular and widely used camera types instead.CCTV security cameras produce images using CMOS or CCD (Charge Couple Device) chips. Tiny, very low price CCTV cameras usually use CMOS technology, produce poor quality images and have very poor light sensitivity. Decent quality CCTV cameras use CCD technology. The size of the CCD chip is normally 1/4″, 1/3″ or 1/2″. As a rule of thumb, the larger the size, the higher the quality of the image produced and the higher the price. However, higher density 1/4″ and 1/3″ CCD chips can now produce as good an image as many 1/3″ or 1/2″ chips.

The number of TV lines in the security camera image is a measure of picture resolution (sharpness). The larger the number of TV lines, the better the resolution and hence, overall picture quality. Standard resolution camera may have 350-380 lines, over 400 TV Lines is generally considered good resolution while over 500 TV lines is considered high resolution. B/W chip cameras produce greater resolution and better light sensitivity, therefore suitable for use in dark areas where light conditions are poor most of the time.On the other hand color cameras offer more realistic and natural picture. CCTV cameras are usually divided into different types based on the body of the camera used.Professional grade cameras.

Have box type body with the ability to use different types and size of lenses. Exchangeable lenses enable this camera, to monitor objects from virtually any distance.Although for indoor use, they can be used for outdoor when combined with weatherproof housing. They are considered to be the most flexible and widely used by professionals for commercial installations.

Bullet cameras. Bullet cameras are, as the name suggest contained inside bullet shaped housing. Most bullet cameras are weatherproof and sealed without the ability to use different lenses. Great advantage of bullet camera is the small size and integrated design, some bullet cameras will even have infrared LED future built-in. Infrared technology is simply LED light in infrared spectrum (not visible to human eye). This light will illuminate viewing area, making possible monitoring in complete darkness. This is great future, but it only works up to certain distance (usually between 10 and 50 ft. depending on model) Vary simple to install and aesthetically designed, bullet cameras are great choice for residential and do-it-yourself installations where monitoring objects are within about 25ft from the camera location (with standard 3.6mm lens).

Board Cameras. Board Cameras are basically fixed lens mounted on a circuit board. These cameras may be packaged in a small case (Mini Cameras) or dome (Mini Dome) or simply sold unpackaged, for mounting by the purchaser. Lenses in these cameras are either of a normal industry aperture or a “pinhole” lens of very small aperture. Pinhole lens cameras are often called “spy” cameras and may be mounted in a concealed way for covert surveillance purposes. The most popular examples of covert board cameras are smoke detector and motion detector cameras.

Since the lenses in board cameras are pre-mounted, have a fixed iris and are usually of a short focal length (i.e. wide angle), their flexibility of usefulness is limited. However, this type of camera can provide a low cost solution in the right situation, particularly in a home environment. We have shortly described most popular types of cameras, lets now discus, how and where they mite be used.

Professional type cameras with C/CS mount lens attachment generally offer best performance and many important futures, like lens control output, Back Light Compensation and many more? Distance from monitoring object to the camera is not an issue, that is why ability to select different lenses, based on camera location is so important. Installation is bit complicated and professional installation strongly recommended. We recommend this type of security cameras for commercial installations.Most Bullet cameras in comparison, do not offer high resolution and lens selection flexibility, but are likely to be weatherproof, some will have infrared light built-in and most of all they are relatively easy to implement.

Bullet cameras usually come with 3.6mm lens witch are considered to be suitable for most standard installations (good for covering small to medium size room or equivalent).For larger roomsor longer distances, cameras with 6mm or higher lens may be required. They are great choice for any do-it-yourself installation. Board cameras in contrast are widely used in covert camera installations, sometimes called Spy Cameras. Many wireless cameras are basically board cameras with built-in transmitter. We are not going to go into wireless cameras right now, as this would be enough material for completely new article.Board cameras are sold as plain circuit board, for integrating into hidden camera devices. They are also available in dome housing, as vary popular Dome Camera or integrated with Smoke Detector, Motion Detector, Exit Sign and so on. Most board cameras also come with 3.6mm lens although some will allow lens to be replaced.

Over the time, most practical design has been Dome Camera with its aesthetic appearance it blends into surroundings, especially with drop down sealing, great for use in stores, lobbies, gas stations and other public places. Practical solution for covert installation are also, Motion and Smoke Detector cameras, they are absolutely not substitute for your security alarm or fire protection. Cameras should always be selected based on the location of the camera (inside/outside), distance from the monitoring object, light condition and budget. When shopping for security cameras, customers are faced with the fact that they will need to select one or another recording device. The days of well-known CCTV time-lapse VCR recorder are almost over. Although some customers still prefer this old fashioned recording solution, it is well worth to invest some extra money to purchase a good quality digital video recorder (DVR). Digital recorder transfers analogue camera video feed into digital format, and stores it on hard drive. T

here are two major types of digital recorders on the market right now .PC Based systems.A special board and software installed on the computer will allow camera inputs and store video on the hard drive. Many people are under the misconception that personal computer with additional hardware installed, will do the job. This explains the hundreds of companies that have hung up a sign, taken out some ads and begun working out of basements and garages, holding themselves out to be DVR manufacturers and security specialists. The main problem with this type of CCTV recorders lies in the main component of it? Yes, it is a computer, designed to do unlimited tasks, but non well. The truth is that any computer based digital video recorder is, and will always be vulnerable to software crashes, hang-ups, system instability, virus related problems etc..?

Stand Alone systems. Very similar in appearance and control functions to standard VCR recorders, are truly remarkable devices. Most video processing is done by hardware, therefore eliminating system crashes, video is also stored on hard drive in digital format. The basic operating system, usually Linux, is permanently stored on special processor, witch is impossible to overwrite or corrupt. Designed and manufactured with single application in mind, it is by far better in performance and reliability to its PC based rival.Some DVR systems will even have remote monitoring capability, useful when monitoring is required in different locations thru Internet or network. Most important futures to look for when selecting the right DVR recorder are motion detection and frame speed. The higher the frame speed the more fluent video recording. Motion detection will allow recording video from each camera only when motion is detected; this is great for extending video recording time. Security Monitors. Video from Security recorder could be displayed on regular TV monitor.

It is OK to do it this way, for baby monitoring or residential application, when quality of the picture is not that important. However for professional installation, security monitors are as much important as cameras. They offer extended life of picture tube (necessary with any static picture, that can cause picture burnout) and much grater resolution. Cables and wiring. Finally any camera installation will require proper wiring. Good quality cable will prevent video degradation over long distance runs. It is recommended to use RG59 or RG6 coaxial cables as it is fully shielded and will prevent video loss up to 400 ft. Coaxial cables will require BNC connectors and proper installation possibly done by experienced technician. In short runs plug and play non-coaxial cables with factory installed BNC connectors may be used (up to 150 ft.). The plug and play cables are easy enough to install by not experienced users.

Cables for CCTV cameras consist of two cables bundled in one jacket. One cable for video and one for power delivery. Conclusion. Every CCTV system is as good and reliable as its weakest component. With this in mind, investing on highest quality and performance cameras, while purchasing low performance recorder, from economical and practical standpoint just does not make sense. For example, why use cameras with 500 TV lines of resolution with monitor that offers only 380 or less. All the benefit of high-resolution camera is affectively sacrificed by limited capability of monitor. Asking questions is important before purchasing video security system, and your vendor will probably be able to give more details and recommend equipment for specific needs and requirements.

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