Cisco Catalyst 4500e Series, Руководство по установке

Страница: 56 / 152

2-2
Catalyst 4500 E-Series Switches Installation Guide
OL-13972-01
Chapter 2 Preparing for Installation
Electrostatic Discharge
Note
See the Site-Planning Checklist at the end of this chapter to help ensure that you complete all
site-planning activities before you install the switch.
Electrostatic Discharge
Electrostatic discharge is common on Category 5E and Category 6 cabling systems.
Category 5E and Category 6 cables have higher capacitance than Category 5 cables. As a result, Category
5E and Category 6 cables can store higher voltages than Category 5 cables and are more prone to
damaging networking equipment if a differential discharge event occurs.
Unshielded twisted-pair cables can store high voltages. When these charged cables are connected to
networking equipment, energy is discharged into the networking equipment; this is known as
electrostatic discharge (ESD). Networking equipment is commonly designed and tested to withstand
common mode ESD events of up to 2000 V. The design for the common mode event is based on the
expectation that the discharge is delivered to all pins of a port at once. Sometimes, voltage is discharged
to some of the pins of the connector and not others, or to some pins on the connector before others. This
is known as a differential discharge event, which can damage the networking equipment being
connected.
You can take the following measures to prevent ESD cable damage:
•
Ground the cable before connecting the networking equipment. You can create a grounding cable
using an RJ-45 patch cable by doing the following:
–
Bare the wires on one end
– Connect the wires to a suitable and safe earth ground
–
Connect the RJ-45 cable to a female RJ-45 connector
• Briefly connect all cables to the grounded cable before connecting to networking equipment.
•
Leave cables from the networking equipment in the distribution closet connected to ports at user
desktops. After you make connections on either side of the cable to networking equipment, the cable
will not build up charge.
Preventing Electrostatic Discharge Damage
Electrostatic discharge (ESD) damage, which can occur when electronic cards or components are
improperly handled, results in complete or intermittent failures. Port adapters and processor modules
consist of printed circuit boards that are fixed in metal carriers. Electromagnetic interference (EMI)
shielding and connectors are integral components of the carrier. Although the metal carrier helps to
protect the board from ESD, use a preventive antistatic strap during handling.
Following are guidelines for preventing ESD damage:
• Always use an ESD wrist or ankle strap and ensure that it makes good skin contact.
•
Connect the equipment end of the strap to an unfinished chassis surface.
•
When installing a component, use any available ejector levers or captive installation screws to
properly seat the bus connectors in the backplane or midplane. These devices prevent accidental
removal, provide proper grounding for the system, and help to ensure that bus connectors are
properly seated.