Corrosion
Corrosion of system connectors is a gradual process that may eventually lead to intermittent failures of electrical
circuits. The oil from a person’s fingers or prolonged exposure to high temperature or humidity may 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.
EMI and Radio Frequency Interference
Electro-Magnetic 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 in the form of 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:
• Always 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.
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:
• 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.
To predict and provide a remedy for strong EMI, consult experts in RFI.
Note
If you use 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 when applicable.
Category 5e, Category 6, and Category 6a cables can store large levels of static electricity because of the
dielectric properties of the materials used in their construction. Always ground the cables (especially in new
cable runs) to a suitable and safe earth ground before connecting them to the module.
Caution
Cisco Catalyst 9600 Series Switches Hardware Installation Guide
18
Preparing for Installation
Corrosion
