Editing Twisted pair (section)

==Cable shielding==
{{Main|Electromagnetic shielding}}
[[File:FTP cable3.jpg|thumb|F/UTP cable]]
[[File:S-FTP CAT 7.jpg|thumb|S/FTP cable]]

Twisted pair cables may incorporate [[Shielded cable|shielding]] in an attempt to prevent electromagnetic interference. Shielding provides an electrically conductive barrier to attenuate electromagnetic waves external to the shield. The shield also provides a conduction path by which induced currents can be circulated and returned to the source via a ground reference connection. Such shielding can be applied to individual pairs or to a collection of pairs. Shielding may be foil or braided wire.

When shielding is applied to a collection of pairs, it is usually referred to as screening, but usage among vendors and authors in applying such words as ''screening'', ''shielding'', and ''STP (shielded twisted pair)'' can be subject to variability.<ref name="anitech">[http://www.anitech-systems.com/MP4000/manual/briefs/ICM-4020E_Hub_Switch_Route_Cable_BR120501.pdf Anitech Systems MP 4000 Manual]</ref><ref name="siemon1">[http://www.siemon.com/us/white_papers/06-07-20-grounding.asp Grounding for Screened and Shielded Network Cabling - Siemon]</ref>

[[ISO/IEC 11801]]:2002 (Annex E) attempts to internationally standardize the various shielding designations for twisted pair (TP) cables using an explicit two-part abbreviation in the form of ''x/xTP'', where the first ''x'' indicates the shielding for the overall cable and the second ''x'' indicates the shielding for individual pairs or quads, where each ''x'' can be:

* U for unshielded,
* S for braided shielding (in outer layer only), and/or
* F for foil shielding.

[[File:10G BASE-T x 3 cables.svg|thumb|F/UTP, U/FTP and F/FTP are used in Cat 6A cables]]

Shielded [[Cat 5e]], [[Category 6 cable|Cat 6/6A]], and [[Category 8|Cat 8/8.1]] cables typically have F/UTP construction, while shielded [[Category 7 cable|Cat 7/7<sub>A</sub>]] and Cat 8.2 cables use S/FTP construction.<ref name="maguire">{{cite web |url=http://www.ieee802.org/3/bq/public/jul15/maguire_25gbt_01_0715.pdf|access-date=2015-09-25|date=2015-07-12 |title=Size of the Category 7A Installed Base|last=Valerie |first=Maguire}}</ref>

Because the shielding is conductive, it may also serve as a path to ground. A foil-shielded, twisted pair cable may have an integrally incorporated grounding wire called a ''drain wire'' which makes electrical contact with the shield. The purpose of the drain wire is for easy connection to terminals which are usually designed for connection of round wires.

Common shield construction types include:
*'''Individual shield (U/FTP)''': Individual shielding with aluminum foil for each twisted pair or quad. Common names: pair in metal foil (PiMF), shielded twisted pair, screened twisted pair, shielded pair.<ref>{{citation |url=https://cdrdv2-public.intel.com/639302/ethernet%20cables%20and%20transceivers%20tech%20guide.pdf |title=Cables and Transceivers Overview |publisher=[[Intel]] |access-date=2024-08-20}}</ref> This type of shielding helps prevent EMI from entering or exiting individual pairs and also protects neighboring pairs from crosstalk.

*'''Overall shield (F/UTP, S/UTP, and SF/UTP):''' Overall foil, braided shield or braiding with foil across all of the pairs within the 100&nbsp;ohm twisted pair cable. Common names: foiled twisted pair, shielded twisted pair, screened twisted pair. This type of shielding helps prevent EMI from entering or exiting the cable.

*'''Individual and overall shield (F/FTP, S/FTP, and SF/FTP):''' Individual shielding using foils for every twisted pair in a cable, and also an outer foil or braided shielding. Common names: fully shielded twisted pair, screened foiled twisted pair, shielded foiled twisted pair, screened shielded twisted pair, shielded screened twisted pair. This type of shielding helps prevent EMI from entering or exiting the cable and also protects neighboring pairs from crosstalk.

An early example of shielded twisted-pair was IBM STP-A, which is a two-pair 150&nbsp;ohm S/FTP cable defined in 1985 by the IBM Cabling System specifications, and used with [[Token Ring]] or [[Fiber Distributed Data Interface|FDDI networks]].<ref name="anitech" /><ref>{{Cite web |url=http://www.techfest.com/networking/cabling/ibmcs.htm |title=TechFest - IBM Cabling System Technical Summary |access-date=2014-01-25 |archive-date=2014-03-11 |archive-url=https://web.archive.org/web/20140311072922/http://www.techfest.com/networking/cabling/ibmcs.htm |url-status=dead }}</ref>

{| class="wikitable sortable" style="text-align: center;"
|+ Common industry nomenclature for cable construction types
|-
! Industry abbreviations
! [[ISO/IEC 11801]] designation{{efn-ua|name=Shield codes}}
! Cable shielding
! Pair shielding
! class="unsortable" | Illustration
|-
| UTP, TP || U/UTP || {{CNone|None}} || {{CNone|None}} || [[File:U-UTP twisted pair cable shielding.svg|150px|U/UTP twisted pair cable shielding]]
|-
| FTP, STP, ScTP || F/UTP || Foil || {{CNone|None}} || [[File:F-UTP twisted pair cable shielding.svg|150px|F/UTP twisted pair cable shielding]]
|-
| STP, ScTP || S/UTP || Braiding || {{CNone|None}} || [[File:S-UTP twisted pair cable shielding.svg|150px|S/UTP twisted pair cable shielding]]
|-
| SFTP, S-FTP, STP || SF/UTP || Braiding and Foil || {{CNone|None}} || [[File:SF-UTP twisted pair cable shielding.svg|150px|SF/UTP twisted pair cable shielding]]
|-
| STP, ScTP, PiMF || U/FTP || {{CNone|None}} || Foil || [[File:U-FTP twisted pair cable shielding.svg|150px|U/FTP twisted pair cable shielding]]
|-
| FFTP, STP || F/FTP || Foil || Foil || [[File:F-FTP twisted pair cable shielding.svg|150px|F/FTP twisted pair cable shielding]]
|-
| SSTP, SFTP, STP, STP PiMF|| S/FTP || Braiding || Foil || [[File:S-FTP twisted pair cable shielding.svg|150px|S/FTP twisted pair cable shielding]]
|-
| SSTP, SFTP, STP || SF/FTP || Braiding and Foil || Foil || [[File:SF-FTP twisted pair cable shielding.svg|150px|SF/FTP twisted pair cable shielding]]
|}

{{Notelist-ua|refs=
{{efn-ua|name=Shield codes|
The code before the slash designates the shielding for the cable itself, while the code after the slash determines the shielding for the individual pairs:
: U{{snd}}unshielded
: F{{snd}}foil shielding
: S{{snd}}screened shielding (outer layer only)
: TP{{snd}}twisted pair
: TQ{{snd}}twisted pair, individual shielding in quads}}
}}