6
EMI
The EMI might be coupled from the source to the firewall through the following coupling mechanisms:
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Capacitive coupling
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Inductive coupling
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Radiative coupling
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Common impedance coupling
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Conductive coupling
To prevent EMI, take the following actions:
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Take measures against interference from the power grid.
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Do not use the firewall together with the grounding equipment or lightning-prevention equipment of
power equipment, and keep the firewall far away from them.
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Keep the firewall far away from high-power radio launchers, radars, and equipment with high
frequency or high current to make sure the EMI levels do not exceed the compliant range.
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Use electromagnetic shielding when necessary.
Lightning protection
To protect the firewall from lightning better, do as follows:
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Make sure the chassis is correctly grounded.
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Make sure the grounding terminal of the AC power receptacle is correctly grounded.
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Install a lightning protector at the input end of the power supply to enhance lightning protection
capability.
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Install a surge lightning protector at the input end of outdoor signal lines to which interface modules
of the firewall are connected to enhance the lightning protection capability.
Rack installation
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Install the chassis in an open rack. To install the chassis in an enclosed cabinet, make sure the
cabinet has good ventilation system.
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Install the chassis on a rack that has rack shelves.
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The rack is sturdy enough to support the chassis and the accessories.
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Reserve at least 0.8 m (2.62 ft) of clearance between the rack and walls or other devices.
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The equipment room is at least 3 m (9.84 ft) high.
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Rack dimensions are sufficient for the chassis.
