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Cisco MGX 8950 Hardware Installation Guide
Release 3, Part Number 78-14147-02 Rev. A0, November 2002
APPENDIX
C
Earthing and Bonding Recommendations
This appendix discusses the techniques and policies that Cisco practices with regard to DC power,
earthing, and bonding of Cisco equipment; and explains why these techniques are the best practice.
More
specifically, this appendix describes the techniques for DC power and earth bonding for the
Cisco
MGX 8950 product range of switches.
This appendix also discusses the principles of mesh bonding and explains the earth return systems that
are used in the Cisco MGX 8950 switches. It identifies the earthing points, shows how they are to be
earthed, and how the DC power connections are to be connected to the equipment.
The earthing and powering techniques described in this appendix are extracts from Cisco internal
documentation, engineering documentation, and the following standards documentation:
• ITU-T K.27, Bonding configurations and earthing inside a telecommunications building.
• GR-1089-CORE, Electromagnetic compatibility and electrical safety—generic criteria for network
telecommunications equipment.
Scope
The bonding and earthing principles adopted by Cisco are as follows:
• Promote personal safety and reduce fire hazards
• Enable telecom signaling with earth return
• Minimize equipment damage and service interruption
• Minimize radiated and conducted electromagnetic emissions and susceptibility
• Maximize tolerance to discharge of electrostatic energy and lightning interference
This appendix supports the principles listed above by providing information that complies with relevant
safety standards on the following topics:
• Bonding and earthing of the Cisco WAN equipment at the telco sites
• Shielding provided by cabinets, cable trays, and cable shields
• Techniques for verifying and maintaining bonding and earthing networks
• Required values of voltage and resistance between different CBN bonding points