Electromagnetic Interference
All the equipment that is powered by AC current can propagate electrical energy that can cause EMI and
possibly affect the operation of other equipment. The typical sources of EMI are equipment power cords and
power service cables from electric utilities.
Strong EMI can destroy the signal drivers and receivers in the chassis. It can even create an electrical hazard
by causing power surges through the power lines into installed equipment. These problems are rare, but could
be catastrophic.
To resolve these problems, you need specialized knowledge and equipment that could consume substantial
time and money. However, you can ensure that you have a properly grounded and shielded electrical
environment, paying special attention to the need for electrical surge suppression.
Radio Frequency Interference
When electromagnetic fields act over a long distance, radio frequency interference (RFI) may be propagated.
Building wiring can often act as an antenna, receiving the RFI signals and creating more EMI on the wiring.
If you use a twisted-pair cable in your plant wiring with a good distribution of grounding conductors, the plant
wiring is unlikely to emit radio interference. If you exceed the recommended distances, use a high-quality
twisted-pair cable with one ground conductor for each data signal.
Lightning and AC Power Fault Interference
If signal wires exceed the recommended cabling distances, or if signal wires pass between buildings, you may
encounter a lightning strike on the chassis.
The electromagnetic pulse (EMP) generated by lightning or other high-energy phenomena can couple enough
energy into unshielded conductors and damage or destroy electronic equipment. For such problems, you must
consult with RFI and EMI experts to ensure adequate electrical surge suppression and shielding of signal
cables in your operating environment.
Rack-Mounting Guidelines
The following sections provide guidelines for selecting racks and precautions for mounting the chassis on a
rack:
Precautions for Rack-Mounting
Follow these rack-mount guidelines to ensure your safety:
• Ensure that the rack is level and stable before extending a component from the rack.
• Ensure that proper airflow is provided to the components on the rack.
• Do not step on or stand on any component or system when servicing other systems or components on a
rack.
• If the rack is provided with stabilizing devices, install the stabilizers before mounting or servicing the
chassis.
Rack Selection Guidelines
Ensure the 2 or 4-post, 19 inches (48.3 centimeters) or 23 inches (58.42 centimeters) rack that you select
complies with the Electronic Industries Association (EIA) standard for equipment racks (EIA-310-D). The
rack must have at least two posts with mounting flanges to mount the chassis.
Cisco ASR-920-20SZ-M Aggregation Services Router Hardware Installation Guide
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Prepare for Installation
Electromagnetic Interference
