Points to consider when designing a CCTV system
A. Purpose of the CCTV system
* Improved security.
* Access control.
* Industrial safety.
* Event recording.
* Management tool.
* After hours monitoring.
* Vehicle or mobile.
* Crime prevention.
* Post-event evidence tool.
* Industrial monitoring.
* Process control.
* B/W or colour.
* Covert or visible.
* Auto iris (outdoors) or manual iris (stable lighting conditions).
* Areas to be covered (by cameras).
* Fixed or PTZ cameras.
* Location and purpose of each camera.
* Distance from the camera to the subject/scene.
* Angle of view required.
* Decide if camera housing needs to be used.
* Type of mounting required ie, pole, wall, ceiling, corner etc
* Availability during required times of operation.
* Position in respect to camera position.
* Localise or centralise power to cameras ie, power each camera individually or altogether from centralised place such as control room.
* Size of PSU is relevant to the number of cameras to be used off it
12 V d.c or 22 V a.c operated equipment (ie, mobile applications)
* Use of UPS?
E. Transmission of video signal
* Via cable, ie, RG59U, power-Ax, twisted-pair, fibre-optic or wireless
* Distance of signal transmission
* Obstacles ie, sharp bends, high voltage equipment, roads/boundaries, different buildings
* Protection of cabling against environment
* Amount of lighting during days and night.
* Direction of sun's position during day.
* Avoid placing cameras directly into sunlight.
* Constant or variable lighting conditions.
* Use of infra-red illuminators/cameras.
* Additional lighting needed?
* Type of light source ie, flourescent, sodium, incandescent, tungsten, sunlight, moonlight, starlight, halogen, mercury vapour etc.
* Indoor or outdoor.
* Marine/coastal area.
* Variation in temperature.
* Need for wiper/washer camera housing.
* Intrinsically safe.
* Highly corrosive.
H. Monitoring and recording location
* A central location to cut down on long cable runs.
* Sufficient clean power available with 24 hour operation.
* Safely secured in event of robbery or tampering by internal staff.
* Sufficient physical space available for equipment and the maintenance thereof.
* Use of recessed or reflective lighting with dimming control to prevent monitor glare.
* Airconditioned and or proper ventilation.
* Monitor/s should be placed directly in line-of-sight of the operator in the seated position (no less than 1,5 m away).
* No more than five monitors per operator.
* Requirement for additional remote monitors in a separate area?
I. Unmanned or manned CCTV site
* If analog system, availability of staff to change tapes.
* PTZ cameras require an operator to be totally effective.
J. Digital or analog recording
L. Communication infrastructure and bandwidth
* Availability of ISDN, PSTN, DSL or leased line circuits.
* TCP/IP routers.
* Bandwidth requirements for amount of cameras and frame rates required.
* Wireless or fixed network.
M. Any existing CCTV
* Integration with existing speed domes, matrix or keyboard controller.
* Use of existing cabling?
A. Camera power
1.) Use only regulated power supplies, the tolerance should be within 5% of the required voltage.
2.) Ensure at least 40% spare capacity per power supply to prevent overheating and voltage loss.
3.) Use power cable of a suitable thickness.
4.) Beware of voltage drops over long distance runs.
5.) Beware of polarity when connecting the power supply to a camera.
6.) Ensure proper cooling or ventilation for power supplies.
7.) Avoid operation of CCTV equipment on the same power circuit as elevators, compressors, generators or any large motors.
1.) Avoid running video cable parallel to AC power cables, especially those carrying high current.
2.) RG59U co-ax runs should not exceed 200 m for colour and 300 m for B/W.
3.) Avoid sharp bends when cabling.
4.) Avoid cable joins and using BNC barrels.
5.) Avoid over-tightening cable-ties.
6.) Ensure use of proper co-ax wire-stripping and crimping tools.
7.) Ensure BNC connectors are properly crimped.
8.) Use rubber BNC boots after crimping to protect crimped area.
9.) Mark or label camera and data signal cables.
10.) Outdoor cable runs should be housed in UV-proof conduit.
11.) In lightning prone areas, install surge protection devices.
C. Camera installation
1.) Test all equipment before installation. Therefore equipment can be replaced before arrival on-site if needed.
2.) Ensure the mounting brackets of outdoor speed domes are properly sealed to prevent condensation in the camera housing.
3.) Use EIA rated RS232/422/485 or CAT-5 cabling for speed dome or PTZ communication.
4.) Avoid direct sunlight on equipment as it raises the temperature of the equipment.
5.) Avoid direct sunlight on equipment as it raises the temperature of the equipment.
6.) Position cameras out of reach of vandals or 'curious' people.
7.) Mount good quality mounting brackets in a stable location to avoid unstable or vibrating images caused by vibration or wind.
8.) CS mount cameras placed inside, at industrial or dusty/damp installations should be placed into outdoor camera housings.
9.) Avoid installing cameras too high above the subject thus preventing 'top-of-head' video images.
10.) Ensure camera mounting poles are mechanically secure to avoid vibration on camera images.
11.) Before connecting power, ensure the supply is 12 V d.c. regulated.
D. Time lapse VCR considerations
1.) Ensure VCR and multiplexer are set at same time lapse speed.
2.) Regular servicing of your VCR will ensure continued operation and quality of recordings.
3.) Use only high quality 'branded' tapes.
4.) Replace tapes after being used 12 times.
5.) Ensure time lapse VCR is suitably hidden in event of a robbery.
6.) Before reviewing a video tape for evidence, make a copy and review the copy. This ensures the quality of the original is preserved, especially when starting, stopping and pausing the tape.
E. Wireless video transmission
1.) For outdoor use, transmitter and receiver must be in line-of-sight.
2.) Determine any possible sources of interference, ie, overhead powerlines, wireless LAN networks, transformers, other transmitters or any other power generating system in close proximity to the transmitter or receiver.
3.) Avoid trees in the transmission path, as branches can cause interference.
4.) Ensure proper alignment between transmitter and receiver.
5.) Beware of lightning. Transmitters are often placed on high masts/roofs, which make them prone to lightning.
6.) Poor weather such as heavy fog and rain can affect transmission.
F. Digital video recorder considerations
1.) It is recommended to connect your DVR and cameras to an uninterruptible PSU (UPS).
2.) Turn-off camera AGC.
3.) Ensure DVR is suitably secure or hidden in event of a robbery.
4.) For PC-based DVRs, regular HDD defragmentation is recommended if DVR is used for other user applications. (Not necessary if PC is dedicated to DVR.)
5.) Ensure enough RAM so that the recording does not get interrupted.
6.) Recording should be on different hard drive to that of the operating system and recording software.
For more information contact Nathan Bearman, Eagle Technology, 021 423 4943.
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