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Cabling
Triaxial Cable
Grounding
Electrical Interference
64
Use triaxial cable instead of coaxial cable when the cable must be routed through an area
having EMI (Electromagnetic Interference) caused by (partial list):
•
Large machinery
•
High voltage power lines
•
Refrigerator units
•
Microwaves
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.
Consult a certified electrician to avoid ground loops—video and audio—in your
Multi-Media LT system. Unbalanced coaxial cable runs between low power sources can
create ground loop problems.
Caution
Do not remove the third wire of the three-prong electrical plug (aka lifting
the ground). This is a violation of local electrical codes.
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 electrical interference on the video signal.
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