Question on steps needed for STP (Shielded Ethernet)

Answered Question
Jan 31st, 2008
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Guys, imagine I need to provide grouding for Cat6 STP cables.


This is a new facility being built. At which stage of the building construction the grounding for this shielded cable should be addressed?


Also, imagine that I have NEMA cabinets across my facility. From those NEMA cabinets the cables will be extended to manufacturing machines across the facility. Should the 'ground' cables be placed in the NEMA cabinet, or next to the manufacturing machines?

Correct Answer by pcameron about 9 years 5 months ago

Generally you ground only one end of a shielded cable. If you ground both ends and there is a potential difference between the two locations, you can have ground currents flow between the sites via the shield. This is called an earth loop - in audio, this causes a humming or buzzing noise. For data, the electromagnetic interference from earth loops can cause data errors or reduce the overall bit rates.


If you have concerns about external interference and using STP to counter it, you really should be considering optical cabling to give total electrical and electromagnetic isolation.


Equipment cabinets are normally grounded as a normal electrical safety measure.


Your building project manager should know these sorts of things!

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Correct Answer
pcameron Thu, 01/31/2008 - 23:34
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  • Cisco Employee,

Generally you ground only one end of a shielded cable. If you ground both ends and there is a potential difference between the two locations, you can have ground currents flow between the sites via the shield. This is called an earth loop - in audio, this causes a humming or buzzing noise. For data, the electromagnetic interference from earth loops can cause data errors or reduce the overall bit rates.


If you have concerns about external interference and using STP to counter it, you really should be considering optical cabling to give total electrical and electromagnetic isolation.


Equipment cabinets are normally grounded as a normal electrical safety measure.


Your building project manager should know these sorts of things!

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