Emi And Radio Frequency Interference - Cisco Catalyst 9200CX Compact Series Hardware Installation Manual

Preparing for Installation
Figure 3: A PCB with Corrosion on its Metal Contacts

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.
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.
Cisco Catalyst 9200CX Compact Series Switches Hardware Installation Guide
EMI and Radio Frequency Interference
15