prinsiples of cctv
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RAKAN KONGSI INFORMASI
A Closed Circuit Television (or CCTV) system is used for
visual (and frequently audio) monitoring and recording
events in a defined area
Generally categorised for the following requirements:
Deter criminal activity Assist in the detection of crime To instil confidence in staff/visitors/customers that
they are in a safe and secure area Provide management intelligence for health &
safety or commercial use
1. What is a CCTV System?
2. CCTV Principles Basic Components of a CCTV System
(Analogue) Old style system with analogue video recording
from a multiplexer. Usually a maximum of 16 cameras per system
Basic Components of a CCTV System (Analogue) Old style system with analogue video recording
through a quad. A maximum of 4 cameras per system.
2. CCTV Principles
Basic Components of a System (Digital)New style system using a DVR to digitally record and playback, usually up to 16 cameras. No multiplexer or quad is required as the DVR performs these functions, amongst others.
CCTV Principles
The Camera CDD Image Sensor (Charged-Coupled Device)
• A group of optical detector integrated circuits • Light is ‘sensed’ by individual photo-diodes (rows & columns of which = ‘pixels‘) • Pixels develop a charge proportional 1/3 inch CCD
to the light level, which are then processed by the camera’s electronics
2. CCTV Principles
There are 3 main types of CCTV camera lens: - Fixed Focal Length (The focal length of the lens cannot be altered) - Varifocal Length (manual zoom length) - Motorised Zoom (Focal length can be automatically adjusted using, for example, a keyboard controller or DVR) >
The greater the focal length, the smaller the angle of view; therefore the image viewed will be larger
Angle of View
Iris Control Methods Auto Iris Features integral circuitry which will vary
the size of lens aperture according to changes in light
Direct Drive Lens control circuitry is within the camera,
rather than the lens (Direct Drive specific lenses and cameras required)
Fixed/Manual Iris No electronic control over the iris
Monitor
Camera housings are designed to protect the camera from weather, dust, vandalism, damage, etc…
Types of Housings :‘IP rated’ Weather Proof Vandal Resistant With or without brackets With or without internal heaters Wash & Wipe
‘IP ratings’ are a measure of resistance to the penetration of solid objects (e.g. dust) and liquids (e.g. rain!)
A product considered to be ‘weatherproof’ would have a rating of IP65 and above
-‘IP’ stands for Ingress Protection - The first number (in this case 6) is the protection against solids (0~6, 6 being dustproof) - The second number (in this case 5) is the protection against liquid (0~8, 8 being protected gainst constant submersion )
Cameras and housings with heaters will require power, mains or low voltage depending upon the product you have chosen.
Where low voltage PSUs are required there are various choices.
24v AV 500MA up to 4A 12v DC 750MA up to 4A
Early CCTV systems used analogue time-lapse VCRs CCTV systems now use DVRs (Digital Video
Recorders) with a huge range of benefits over old analogue technology
Many existing installations, therefore, are upgrading their recording system from analogue VCR to DVR
The benefits of DVRs: Digital image quality No need for tapes (changing / storage of) Fast, easy image search & retrieval •
Remote viewing & control capabilities Never stops recording • Up to 400 images
per second (IPS) record rate Up to 1.5TB storage Easily providing in excess of 31 days storage Less mechanical components to service >
Main factors for consideration in choosing the
correct DVR: Number of cameras Record rate (images per second) HDD size (amount of data storage) Remote viewing / control Fixed / Mobile Data transfer/storage media formats
Choosing recording frame rate:
Each DVR has a maximum IPS rate (100, 200, 400)
The IPS rate is normally divided by the number of channels ie. 400 IPS, 16 channel recorder would record @ 25 IPS per camera
High quality DVRs allow control of IPS rate per camera channel
How long does the customer require to retain the images/video on the DVR?Record duration is the ‘data lifetime’ of the recorded images / video on the DVR Data lifetime will be determined by customer’s
specific requirements and rules of the Data Protection Act
Longer data lifetimes require larger HDD space
Estimating record duration, the following all
Need to be considered:
Number of camera channelsHard Drive size IPS rate Compression type
Multiplex (Simultaneous functionality) :Simplex: The ability to record or playback but not at the
same time. For live view it is only possible to see a single camera on the monitor, multiple camera view is possible during playback.
Duplex: The ability to record and playback simultaneously. Multiple live screen is possible. However, the monitor will only display live images or recorded images.
Triplex: The ability to record and playback simultaneously. Multiple live screen is possible and unlike Duplex operation the monitor will display both live images and recorded images simultaneously.
Angle of view Internal or external Static or PTZ Colour or Monochrome High or Low resolution Available / Changing light
levels Site orientation Power availability Data Protection Act
Alarm Inputs send telemetry signals via the DVR to automatically control / preset camera position, record rate, image resolution, etc…
Alarm Inputs triggered via:
• External detection devices • Panic Button • Access Control Equipment
Lamps are usually Tungsten Heat generated by the bulb’s wasted
energy Aluminium-plated reflector Short life High power consumption / High cost of
ownership Range = various angles – Wide /
Medium / Narrow
Use solid state technology Long life Better performance & efficiency Gold-plated reflector Low power consumption Need IR sensitive cameras Range = 10° ~ 60° / 20m ~ 175m >
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