Dust And Particles; Corrosion; Electromagnetic And Radio Frequency Interference - Cisco 6503 - Catalyst Firewall Security Sys Installation Manual

Chapter 2 Preparing for Installation

Dust and Particles

Fans cool power supplies and system components by drawing in room temperature air and exhausting
heated air out through various openings in the chassis. However, fans also ingest dust and other particles,
causing contaminant buildup in the system and increased internal chassis temperature. A clean operating
environment can greatly reduce the negative effects of dust and other particles, which act as insulators
and interfere with the mechanical components in the system. The standards listed below provide
guidelines for acceptable working environments and acceptable levels of suspended particulate matter:
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Corrosion

Corrosion of system connectors is a gradual process that can eventually lead to intermittent failures of
electrical circuits. The oil from a person's fingers or prolonged exposure to high temperature or humidity
can corrode the gold-plated edge connectors and pin connectors on various components in the system.
To prevent corrosion, avoid touching contacts on boards and cards, and protect the system from extreme
temperatures and moist, salty environments.

Electromagnetic and Radio Frequency Interference

Electromagnetic interference (EMI) and radio frequency interference (RFI) from a system can adversely
affect devices such as radio and television (TV) receivers operating near the system. Radio frequencies
emanating from a system can also interfere with cordless and low-power telephones. Conversely, RFI
from high-power telephones can cause spurious characters to appear on the system monitor. RFI is
defined as any EMI with a frequency above 10 kilohertz (kHz). This type of interference can travel from
the system to other devices through the power cable and power source or through the air like transmitted
radio waves. The Federal Communications Commission (FCC) publishes specific regulations to limit the
amount of EMI and RFI emitted by computing equipment. Each system meets these FCC regulations. To
reduce the possibility of EMI and RFI, follow these guidelines:
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When wires are run for any significant distance in an electromagnetic field, interference can occur
between the field and the signals on the wires. This fact has two implications for the construction of plant
wiring:
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OL-5781-08
Network Equipment Building Systems (NEBS) GR-63-CORE
National Electrical Manufacturers Association (NEMA) Type 1
International Electrotechnical Commission (IEC) IP-20
Only operate the system with the chassis covers installed.
Ensure that all chassis slots are covered by a metal filler bracket and that an unused power supply
bay has a metal cover plate installed.
Ensure that the screws on all peripheral cable connectors are securely fastened to their
corresponding connectors on the back of the chassis.
Always use shielded cables with metal connector shells for attaching peripherals to the system.
Bad wiring practice can result in radio interference emanating from the plant wiring.
Strong EMI, especially when it is caused by lightning or radio transmitters, can destroy the signal
drivers and receivers in the chassis, and even create an electrical hazard by conducting power surges
through lines into equipment.
Catalyst 6500 Series Switches Installation Guide
Site Requirements
2-15