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Multi-Media Unit: Installation Instructions
6.2.3
Electrical Interference
To manage electrical interference (also called electro-magnetic interference or EMI), you
can survey the facility for electronics that generate EMI "noise"—fluorescent lights, radio
frequency (RF) receivers or transmitters, power lines or elevator shafts—before installing
equipment. Cables can be routed around or away from sources of noise so that there is
no interference with the CCTV signal.
Hum bar
Hum bars appear as horizontal distortion across the monitor. The hum bar is caused by
the effect of high voltage on the horizontal synchronization signal.
Triaxial cable
Use triaxial cable instead of coaxial cable when the cable must be routed through an
area having EMI caused by:
Triaxial cable has a center conductor, insulator, and shield, followed by a second
insulator and shield. The double shielding significantly reduces the amount of EMI
radiation that is exposed to the center conductor.
6.2.4
Lighting
A big factor of image quality is the amount of light reaching a camera's lens. You can
manage lighting by moving the CCTV cameras in consideration of:
6–4
large machinery
high voltage power lines
refrigerator units
microwaves
- and so on -
beam angle from the light source to the camera lens
intensity of reflection and contrast from objects in a camera's field
- and -
complexity and motion at the scene.
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