If the camera or cameras are to be used outdoors then black and white cameras are more suitable, as they need less light to form a useable picture.

Colour cameras are more suitable for indoor applications where light levels are higher.

Most CCTV cameras use a CCD (Charge-Coupled Device) light-sensitive chip to capture the image The sensitive area is split into a large number of picture-elements or ‘pixels’.

The size of the CCD chip is known as the ‘format’ which may be ½”, 1/3”, ¼” or 1/6”. In general, the larger the format the better the low-light pictures will be. With the latest generation of CCDs, 1/3” cameras will give good results in most situations.

An image from a scene is focused through a lens onto a chip surface, charge is built up in each pixel proportional to the intensity of the light falling on to it. Hence an electrical representation of the optical image is formed. Typical pixel counts for CCD sensors are between 250,000 and 500,000.

Note that the majority of manufacturers supply their cameras without lenses fitted – REMEMBER TO QUOTE FOR THE LENS!

The main performance criteria of a camera are its sensitivity and resolution.

Sensitivity is a measure of the minimum amount of light required by the camera to generate an acceptable image. Resolution defines the amount of picture detail in the image produced by the camera.

Day-Night cameras provide a colour picture when there is sufficient light to do so, normally during daylight hours. When light levels fall, the picture reverts to black and white, to take advantage of the inherently better sensitivity performance of monochrome cameras.

Monochrome cameras typically require approximately 1/10 of the amount of light to make a useable picture, compared with a good quality colour camera.

The switching from colour to monochrome at dusk, or from mono to colour at dawn can either be automatic, using the camera itself as a light level meter or it can be controlled via an external photocell or a contact from suitable telemetry equipment.

In order for colour cameras to reproduce colours accurately they are normally equipped with an infrared cut filter. This prevents infrared light getting onto the CCD imaging device.

Natural daylight is a mixture of both visible and infrared light. If a colour camera is exposed to infrared light, the image will be lighter than if it was producing it from the available visible light. Hence colours would appear whitened; red objects would appear pink. Grass, being reflective to infrared light, would appear a pale shade of green.

Not all Day/Night cameras are the same; there are three distinct types.

One does not have an infrared cut filter fitted. Digital or other signal processing is used to compensate and make colours look correct when in day mode. This type of camera has good sensitivity at night and can be used with infrared lighting.

A second choice of Day/Night camera comes fitted with an infrared filter. This gives good colour rendition in daylight, however the camera is not as sensitive as a monochrome camera. The camera is not as sensitive to infrared and cannot be used with infrared illumination. If lighting is required, which is likely given the cameras reduced sensitivity; only visible lighting can be used.

Clearly, it would be appropriate if the infrared filter was in the optical path during daylight to give good colour rendition. It would also be best if there was no filter in place at night so that the camera is as sensitive as a normal monochrome camera, therefore it would be sensitive to infrared light, enabling overt or semi-covert surveillance.

Finally, there are Day-Night cameras, for instance the VCP501 Zoom camera from Videcon, which physically move an infrared cut filter in and out of the optical path to give true colour rendition in daylight, and low light and infrared sensitivity at night.

Because of there different wavelengths, infrared and visible light focuses at different points behind the lens. It is often a problem achieving a sharp image in both day and night modes. When using a standard auto-iris lens on a Day-Night camera, always perform the back focussing at the lowest light levels when depth of field is at a minimum.

Warranty

Branded CCTV components are highly reliable and are expected to deliver on their promises. However, even if there are any faulty products, these are most likely to fail within the first 90 days of use which is within the manufacturer’s warranty period. Therefore, purchasing extended warranty coverage may not be required.

Maintenance:

It is advisable to consider an appropriate maintenance plan for the CCTV system. A fairly-priced maintenance contract can go a long way in increasing the life of the CCTV system. Moreover, cleaning and maintaining the product on a regular basis can detect and keep major problems at bay.

Legal issues:

Use of dummy cameras to deter offenders may backfire and cause legal issues. It is also important to note that it is illegal to tape audio. People can be monitored without consent but taping voices is considered an intrusion on privacy.

Need-gap:

Understand your exact needs before purchasing a CCTV system. Purchasing a high end product for basic security needs will obviously be a waste of money.

Demonstration:

Get a demonstration of the CCTV in office settings from the dealer; it is the best way to evaluate the effectiveness of the system you are planning to buy.

Positioning of cameras:

Most people want to make the camera position as discreet as possible. The modern bullet-type camera is no bigger than your small finger in length and can easily be located under or on the fascia/soffit boards where the roof line meets the wall. This location also provides good shelter from wind and rain and can be shaded from excessive sunlight. The height of the camera position will give a good area of view and minimise the risk of vandalism.

However, another advantage of this location is cabling. It is usually easy to run the cables into the loft from this position. Many houses have a small ventilation gap between the roof tiles and the external wall, or a small hole may be drilled in the fascia board to gain access to the loft.

Cabling:

It is usually easy to pick up mains power in the loft or at least if additional cabling is required it is now internal. Wireless transmission can be used for the video signal with the receiver being placed next to the monitor or recorder (TV, VCR, PC etc.). That's it, installation complete.

A hard-wired system can almost be as easy to install. Locate the TV aerial down-lead that may be in the loft or run down the outside of the house. It is usually possible to run the CCTV camera video cable alongside the aerial cable, which will lead directly to the TV.

A neat method of connection is to use an RF modulator. This little box changes the camera\'s video output to an RF output. This means you can pipe the CCTV images down the existing TV aerial down-lead and view on the TV/VCR as if it were another channel. If the house is fitted with a TV aerial distribution system, this method of connection allows the camera pictures to be viewed on all TV sets.

Addition of Switchers:

Consider placing switchers, multiplexers or DVRs in the loft. This contains all the camera cabling in the loft with just one output cable to a monitor. It also hides away the recording device.

For servicing and some maintenance of the alarm system, a specialised technician may be required.

However there are some basic steps you can take to minimise not only false alarms but also repeat service calls by those responding to your alarm.

• Ensure spider webs are cleaned away from the
  sensors and other alarm equipment.
• Avoid leaving pets inside when the alarm is activated
  (internal audible sirens can cause pets undue distress when activated).
  
• Consider an effective pest control program as vermin
  and birds can cause a false alarm activation.
  
• Close windows and doors and switch off air conditioners as drafts can move items causing them to be detected by alarm sensors.
  
• Avoid hanging mobiles/decorations and other items from the ceiling as these can trigger a false alarm activation.
  
• Ensure an alarm technician completes periodical services.
  
• Ensure all users of the alarm are competent in operating the system.
  
• Conduct regular system tests (monthly).
  
• Advise the monitoring company of any changes to
  users or the system.
  
• Repair any problems immediately.
  
• Change alarm codes on a regular basis or when there is a change in users.
  
• Ensure duress buttons are located in a position that cannot be easily bumped by people or other items.