Cisco Systems SFS 7000D Manual De Usuario

Exhaust fans cool power supplies and system fan trays cool systems by drawing in air and exhausting 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. In addition to regular cleaning, follow these 
precautions to avoid contamination of your equipment:

Do not permit smoking anywhere near the system.

Do not permit food or drink near the system.

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.

EMI and RFI from a system can adversely affect devices such as radio and 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 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 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: 

Operate the system only when the chassis cover is installed. 

Ensure that all expansion slots are covered either by a card-mounting bracket or by a metal filler 
bracket and that all drive bays have either a drive or a metal insert 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 remedy strong EMI, you might need to consult experts in RFI.