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SOME SIMPLE RULES:
Over the past few years CCTV has
had a major impact on crime detection and prevention, and has never
been out of the news for long. CCTV is also useful management tool and
ensures best working practices and Health and Safety requirements are
met. The innovation of Digital Technology has improved the day-to-day
management and quality of archived video. However, basic rules must be
followed in the design of the system if the video is to be used as
evidence and to be of value at a future date.
The following rules will assist
the designer to select the correct camera with the correct focal length
and light tolerance capabilities for most simple installations:
1. Produce a plan view of the
site showing the areas, which require CCTV coverage. Mark the plan with
approximate dimensions of buildings open areas and perimeters. This
will allow you to calculate the approximate numbers of cameras required
and the relative mounting positions for internal and external cameras.
2. Select a suitable location for the control equipment. For reasons of
compliance with Data protection Law and so that evidence cannot be
easily removed from site the Video recording equipment should be
installed within a locked room or placed within a locked cabinet.
3. When selecting suitable camera types consider the following:
· Is the camera inside or outside? External cameras require protection from the environment.
· What is the lighting conditions affecting the camera view. Is sufficient lighting for colour cameras?
· Consider the type of lighting to be used i.e. white halogen or Meta halide lighting for colour cameras.
· Would cameras that operate in very low light conditions be
better such as Day Night cameras or would Monochrome or Night Vision
cameras be more suitable
· If fixed cameras are to be used which lens will be most
suitable for the size of image required on screen during live view and
playback. If in doubt affordable cameras with built-in manual zoom
lenses are now available. This enables the installer to adjust to the
perfect picture during installation
· Is the camera low enough to be attached by vandals? Special
cameras and cages are now available to protect cameras from damage.
Home office guidlies for recognition of persons.
4. Consider the size and
position of monitors. Are they best desk or wall mounted? Are they
large enough to be seen without eyestrain?
5. Getting the video signals from the cameras to the recording
equipment. Consider the type of cables to be used and how the cameras
will be powered.
· Where will the cables be routed.
· Inside buildings? Outside buildings?
· Within underground ducting?
· What type of cable to use? This is normally determined by
distance. 50 to 100 meters shotgun coaxial cable is best and most
economical. Over this distance data cable CAT5e is good, especially if
there are more than 8 cameras on the system. If distances are over 1000
Meters fibre optic cables may be more suitable.
6. Now the selection of suitable
Digital Video Recording Equipment from the wide range available. Make
your selection based on current and future requirements for numbers of
cameras and audio feeds to be archived. How quickly you want to record
(from 1 to 25 images per second per camera), the quality of the
recorded image (size of image retreaved from the archive) and most
importantly the size of archive storage (how long the video will be
kept before it is overwritten. Location for the DVR (Digital Video
Recorder), installed within a locked room or within a locked cabinet.
DVR should be kept secure to comply with Data Protection Guidlines.
Finally, can the system be
simply maintained and cleaned. CCTV system images are of no use as
evedence if the lens was dirty or the recording system failed when an
incident occures.
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