CCTV is a large topic and so we can only provide a broad overview, but if you are intending to obtain quotations then why not telephone us. Our surveys are generally free of charge and we can often provide some guidance over the phone

Mid sized to large organisations are generally able to justify in house security experts or the services of external security consultants. However, for small organisations, such as schools, clubs, smaller business premises and owner/manager retail outlets, the task of preparing security specifications and assessing quotations frequently falls on untrained shoulders.

Best Laid plans…
Despite the availability of information, many CCTV systems fail to meet the expectations of the customer because they were either poorly designed; the expectations of the customer were unrealistic, or the limitations not made clear.

Start with a simple statement of objectives. What do you want to do with the system? For instance do you want cameras just to detect intruders? This will have an impact on the number of cameras and their coverage.

Identify the critical places or risk areas that you want to monitor and decide on whether to monitor during day only or day and night. Lighting requirements are another frequently overlooked factor, which we will come to. If you have a plan or layout of the building this helps greatly during the survey to mark camera positions and show coverage.

Problems arise with CCTV when the expectations for identification of the subject are not met. Typical reasons for this are:
:: The field of vision is too great for the camera.
:: Lighting levels are not adequate
:: Sunlight is causing flare or silhouetting
:: The camera or recorded image quality is simply not adequate for the requirements
:: The recorded frame rate is not sufficient to capture the event

Much of this can be ironed out by a simple statement of what you are intending to obtain from the system and a discussion with your installer as to what can be realistically achieved. We frequently provide advice on camera types and location during our surveys. We can also show you camera samples and demonstrate our digital video recorder when requested.

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Camera Positioning and Coverage

A scale plan of the location is always a help and can save a lot of time during the survey.

Don’t try to cover too large an area with a single camera. An area such as a car park with only one or two cameras will result in tiny objects being recorded which cannot be identified.

Please remember that only a limited amount can be achieved through image enhancement, mainly contrast improvement or edge detection. You cannot create definition that is not already present, thus zooming the image post capture will only result in a larger grainy image without improved detail.

The references included below describe how to define the field of view. Identification requires around 120% subject coverage. That equates to a field of view filled by about 83% of the subject. Recognition generally requires the subject to occupy at least 50% of the camera field of view.

Figure 1: Ensure the field of coverage is sufficient for your needs

Make sure that you have identified access points. The number of cameras will be dependent on the number of areas you want to cover and the level of detail you wish to view and record.

Crossing beams will help identify suspects from more than one aspect, so that a subject facing away from one camera can be visible to another. Cameras should be positioned at a reasonable height to prevent tamper, but not at too sharp an angle so that only the top of subject’s head can be viewed.

Camera mounting stability is important, which is the reason that CCTV columns appear to be far more sturdy than they need to be to support a small camera. If the column flexes in the wind then the camera may not be able to focus and the movement sensing will be continuously activated. At a zoom factor of 25:1, a 1mm movement at the camera lens will result in a 1inch movement at the subject, which is one of the reasons why cameras should not be fixed to trees.

Check current and potential tree and vegetation growth. A frequent problem arises when tree growth over a period of time obscures the camera field of view.

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TYPES OF CAMERA

:: Analogue Cameras

Static Dome Cameras
These have become very popular in the last few years as new vandal resistant models have become available and image quality approaches that of the conventional box camera. Most vandal resistant domes can take the shock of a 4lb hammer, which will stop all but the most aggressive attacks. They are good for unobtrusive monitoring for example in corridors and classroom areas, but also have the advantage that you can’t easily see which way they are pointing and thus any dead areas (outside the field of view) can’t be easily identified.

Figure 2: Static Dome Camera

Figure 3: Cameras installed in school corridor for unobtrusive monitoring

Pan Tilt Zoom (PTZ) Cameras
These are known as fully functional or Pan Tilt Zoom cameras, and are controlled either by channelling the signal down the video cable or via a digital interface called RS485. They enable a camera to tilt and rotate, usually through 360 degrees and zoom by mechanical lens movement to locate a subject. Most city centre cameras are of this type.

Beware of specifications which quote super high zoom factors, generally these figures relate to digital zoom. Optical zoom is what you are looking for, which is achieved by moving the lens position. Digital zoom tends to produce a pixelated effect. The image loses definition because it is generally just digitally enlarged within the camera. A factor of x18 to x27 optical zoom is good for most general applications.

PTZ cameras of course can only look in one direction at a time, and generally rely on an operator to position them. In the hands of a skilled operator they can be very effective at tracking activity for example in city centre monitoring. However all too often they are positioned on the corner of a building or car park and spend their life on automatic tour with little chance of picking up any useful activity, which is why there are frequent complaints that the camera was looking the other way when incidents take place.

Where the camera does not have an operator to control movement, strategically positioned detectors such as passive infra red (PIR) detectors can often be used to automatically direct the camera’s eye to a pre-programmed or “preset” position for instance over one of several entrance ways. This technique generally applies to intruder detection applications, such as monitoring the perimeter of a large warehouse, and would not be suitable for controlling cameras in busy locations.

We installed a PTZ camera at the Will Adams pupil referral centre to cover the large flat roof where youths were frequently found to climb onto and cause damage. Part of the camera’s routine tour views the roof area to record any suspicious behaviour

Figure 4: Pan Tilt Zoom Camera

Box Cameras
These are the traditional camera style mounted in a box case. They are popular because they support a wide range of interchangeable lenses and technical specifications. Types of camera are as diverse as the applications to which they are applied. For this reason we won’t go into too much detail in this guide.

For most applications, both internal and external, the camera is installed in some form of housing. For external applications these require in-built heaters to prevent condensation build-up. When used for internal installations they help to prevent dust build-up on the lens and protect the camera from damage.

Figure 5: Standard CCTV Camera and Housing

Day/Night Switching Cameras
These cameras are a new generation, which have proved very popular in providing the best of the colour camera for day operation with the low light performance of the monochrome camera for night use. They incorporate an infra-red cut filter which shields the camera from sunlight, but is automatically removed at night to allow operation with infra-red illumination and improve low light performance. They can operate very well at light levels below “dusk” to the point where it is hard for people to see, and thus go a long way toward reducing the impact of providing adequate lighting.

:: Digital Cameras

Mega-Pixel Cameras
A fast emerging and important new market is the mega-pixel camera. This all digital camera provides higher definition images than conventional CCTV cameras ranging up to 2500x 2000 pixels. Most transmit the image data via network IP interfaces or USB digital interfaces. They are currently significantly more expensive and require specific recording techniques, so are predominantly used for specialist projects for example police forensics, football stadium crowd monitoring and vehicle damage recording.

Two types of sensor are available CMOS and CCD. The CMOS sensor is most widely available in the lower cost cameras and generally produces a lower quality image to that of the equivalent CCD sensor, However they will become more widely accepted as volume increases.

IP Cameras
IP cameras transmit digital images directly between other networked devices such as a computer with installed recording software. Transmission takes place across a local or wide area network via standard network cabling such as CAT-5 or fibre optic cabling. They benefit by allowing greater flexibility in routing the image data rather than linking all cameras to a single central point for recording and monitoring.

The image compression is generally carried out within the camera and so the need to multiplex or switch between cameras at the recorder is removed. As a result, you can achieve faster frame rates than a multiplexed system given sufficient network bandwidth.

Since the data is addressable, you can route more than one camera down a single cable using a network switch. IP cameras are also independent of the traditional analogue video standards such as PAL or NTSC. This means that they provide a suitable platform for the newer mega-pixel cameras, which are becoming available from manufacturers.

IP cameras have been criticised for taking excessive network bandwidth when used in conjunction with the general office networks and carry a cost penalty and restrictions in product selection when compared to conventional analogue output cameras. Their advantages should be carefully considered before installing them as the “latest thing to have”. Combinations of the two technologies can also provide an effective solution when used with care.

See the detail of a 2500x200 Camera

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SHEDDING LIGHT ON THE SUBJECT

:: Artificial Lighting

Lighting is one of the most under-resourced components of a CCTV system and is a field of expertise in itself. It is relatively easy to obtain a good image from a camera during the day. However at night the situation is very different. For security applications night-time is frequently the highest risk period, and a system which cannot see in the dark is of no value.

If you need night monitoring, you need to consider lighting choices as well as the type of camera at the project design stage. There are two main sources of light used for security applications, white light and infra-red light.

White light is widely known in its standard form of the security halogen spotlight. It is relatively inexpensive for most basic applications, but should incorporate some form of lighting controller so that it switches on at night only and is activated by an event such as movement. Unnecessary lighting contributes to light pollution, is frequently annoying to any neighbours and is wasteful in energy.

Infra-red lighting is invisible to the human eye and can therefore be used where white lighting is not practical, for example where white lighting would cause annoyance or could dazzle motorists. Infra-red is more efficient than white light for CCTV cameras and therefore lower power levels can be used to achieve the same visibility.

For internal use, simple low power security lighting may be all that is required to lift the light level to about 1 Lux over the area of interest.

Good lighting is one of the best deterrents to intruders and is re-assuring for staff for example when leaving a building at night for the car park. Burglars like dark places to operate. However it should be noted that if cameras are reliant on lighting for night operation, then lighting becomes a critical component of the CCTV system and needs to be regularly maintained. Halogen bulbs and infra-red bulbs last about six months, whereas infra-red LED matrices are typically guaranteed for five years, but naturally have a price premium.

Figure 6: Infra-red illumination in conjunction with day/night switching cameras can prove very effective at night.

Figure 7: Infra-red illuminator

:: Sunlight

The effect of natural light has a very significant impact on the positioning of both internal and external cameras. A camera looking down a corridor with a glass doorway at the end can be affected by sunlight causing silhouetting of the subject against a light background. Alternatively cameras looking directly into sunlight will cause flaring of the image.
Sunlight can be mitigated to an extent by sun visors and backlight compensation. The most effective solution is to choose where possible the best camera position with the sun shining from behind the camera.

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POWER SOURCES

Camera power requirements can be divided into low voltage (12vDC or 24vAC) or mains voltage. In the past the majority of cameras were mains powered. However it has become more commonplace to distribute low power cabling or use up-the coax or power over Ethernet to supply the camera power. This has the advantage that all the power sources are contained within a central point and therefore a single uninterruptible power supply (UPS) can keep the entire system operational during mains power loss. Maintenance of the power unit is easier and installation costs for running low voltage cabling are lower than the alternative fused spur mains power outlets.

There is a trend towards the use of 24vAC as the low power source, which travels further and is more efficient than 12vDC.

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TRANSMISSION

This section on transmission deals briefly with the interface between the camera and recording/monitoring device.

:: Cabled

Twisted pair or network cabling is a fast growing alternative to coaxial cable. This method uses a “balun” media converter connected to the camera. The analogue video signal is then transmitted via network cabling to the receiver. The receiver unit then converts the signal back to 1volt peak to peak ready for connection to the monitor recorder unit. This method can be cheaper and less bulky to install than coaxial cable and can be used over distances in excess of 1km using “active” components, whereas coaxial cable is generally limited to about 300metres.

Twisted pair transmission can also be readily mixed with coaxial cabling, so that you can use CAT-5 cabling for certain cameras and coaxial for others without penalty. There is also no restriction on the camera type since this technology can be connected to all coaxial compatible cameras.

We installed twisted pair transmission cabling at the Quakers head office in Euston. The property is a large prestigious Grade II listed building which required special care to ensure cabling was neat and unobtrusive. We chose NVT twisted pair technology to reduce cabling clutter and cope with the long interconnecting corridors ensuring good signal quality over the distances between the cameras and recorders.

Figure 8: NVT video transmission using CAT-5 cable

IP Cameras transmit digital data directly from their output as a data stream, and are therefore designed to operate over a digital network. These cameras require CAT-5 or fibre optic cabling between the camera and recorder/viewing station.

Caution needs to be applied when considering operating IP cameras across networks shared with other network users. Networks can “go down” and users or applications can be prevented from gaining access to the network either by intent (not necessarily malicious) or inadvertently. As an example, if the CCTV system effectively competes for scarce bandwidth with other vital data such as financial information, the CCTV system could be temporarily suspended from access to the network and not re-instated until it is too late following an incident. This may be especially true if the network administrator is not responsible for the CCTV system and the security manager is not familiar with IT networks.

The best way to ensure that transmission between the camera and recorder is not interrupted is to have a dedicated link via one of the following options:
:: A dedicated IP network
:: Direct connection via CAT-5 using video baluns (analogue transmission over twisted pair)
:: Direct connection via coax
:: Direct connection via Ethernet over coax
:: Dedicated IP based telephone line such as TCP/IP over ISDN

“IP over coax” is a further technique based on our own patented design for transmission of IP video over existing coaxial cable. This allows your existing coaxial cable to be re-utilsed as a general purpose digital highway for transmission of IP Camera data or other networked devices. Our data sheet is available on our web site at the following link. Data Guru shows how existing cabling can be “recycled” for use as a digital network when upgrading from analogue transmission to digital IP transmission.

:: Non-Cabled

Most radio systems operate on very high frequency (2.4GigaHtz) or greater. The technology is expensive and because transmission requires a separate channel for each camera, you can only transmit up to about 4 cameras per site. However the benefits are very apparent when considering, for example, receiving video images from an offshore lighthouse.

We installed wireless transmission at a marina to relay video from the entrance barrier back to the main offices. Despite lifting cranes crossing the transmission path, the video signal remained unaffected.

Figure 9: Wireless video transmission across a busy dockyard

Wireless Network
Wireless CCTV networks are based on widely available wireless network hardware. Using this technology you can create a dedicated network of IP cameras. If coverage and network reliability is good then this can provide a very cost effective means to connect IP cameras and recording software, particularly across awkward transmission paths such as a roadway. Unlike the analogue equivalent you are not limited to the number of channels, since IP Cameras are addressable. Thus capacity is limited by the available network bandwidth only.

3-G
It would be really good to be able to place a camera anywhere in the country and receive video at any distance regardless of line of sight. With 3G you can do this! It’s not all that straightforward, coverage is an issue and you have limitations on the amount of data you can send. The best way to overcome this is to only transmit on specific events, for example on detection of movement. However it is an exciting technology, especially for mobile hot spot monitoring.

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RECORDING

Of all the considerations with a CCTV system recording is probably the most diverse and hotly contested subject to deal with. There are many recorders from dedicated boxes to personal computer based systems to networked software solutions, each with a range of pricing alternatives. On the one hand the user has a wide choice, on the other hand selection without expertise would be a confusing option.

As a first point we would always recommend that you try out or see a demonstration of a new recorder. No matter how good the technology, if the user interface is too complicated or does not provide sufficient features for your current and foreseeable requirements, then you will be at risk of having to change probably the most expensive single item in the system. We have provided a short checklist, which is far from complete but provides a framework to build your own specification.

Figure 10: Computer based DVR and software with graphical interface

Figure 11: Dedicated recorder unit with push button interface

USEFUL LINKS

There are also many sources of free information, a few of which are included in the following links:
Information Sources:
The Information Commissioner's Small User Check List
UK Police Requirements for Digital CCTV
HOSDB CCTV Operational requirements manual

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