Editing Ethernet over twisted pair (section)

== Cabling ==
[[File:Rj45plug-8p8c.png|thumb|240px|[[8P8C]] modular plug pin positioning]]

{| class="wikitable" style="float:right;clear:right;margin-left:1em"
|+ [[ANSI/TIA-568]] T568A termination <!--standard name is 'B' termination options are 'A' or 'B'-->
! Pin !! Pair !! Wire{{efn|name=tipring|The terms used in the explanations of the 568 standards, [[tip and ring]], refer to [[Phone connector (audio)|older communication technologies]], and equate to the [[Electric charge|positive and negative]] parts of the connections.}} !! Color
|-
| 1 || 3 || tip
| [[File:Wire white green stripe.svg|60px|Pair 3 Wire 1]] white/green
|-
| 2 || 3 || ring
| [[File:Wire green.svg|60px|Pair 3 Wire 2]] green
|-
| 3 || 2 || tip
| [[File:Wire white orange stripe.svg|60px|Pair 2 Wire 1]] white/orange
|-
| 4 || 1 || ring
| [[File:Wire blue.svg|60px|Pair 1 Wire 2]] blue
|-
| 5 || 1 || tip
| [[File:Wire white blue stripe.svg|60px|Pair 1 Wire 1]] white/blue
|-
| 6 || 2 || ring
| [[File:Wire orange.svg|60px|Pair 2 Wire 2]] orange
|-
| 7 || 4 || tip
| [[File:Wire white brown stripe.svg|60px|Pair 4 Wire 1]] white/brown
|-
| 8 || 4 || ring
| [[File:Wire brown.svg|60px|Pair 4 Wire 2]] brown
|}
{| class="wikitable" style="float:right;clear:right;margin-left:1em"
|+ [[ANSI/TIA-568]] T568B termination <!--standard name is 'B' termination options are 'A' or 'B'-->
! Pin !! Pair !! Wire{{efn|name=tipring}} !! Color
|-
| 1 || 2 || tip
| [[File:Wire white orange stripe.svg|60px|Pair 2 Wire 1]] white/orange
|-
| 2 || 2 || ring
| [[File:Wire orange.svg|60px|Pair 2 Wire 2]] orange
|-
| 3 || 3 || tip
| [[File:Wire white green stripe.svg|60px|Pair 3 Wire 1]] white/green
|-
| 4 || 1 || ring
| [[File:Wire blue.svg|60px|Pair 1 Wire 2]] blue
|-
| 5 || 1 || tip
| [[File:Wire white blue stripe.svg|60px|Pair 1 Wire 1]] white/blue
|-
| 6 || 3 || ring
| [[File:Wire green.svg|60px|Pair 3 Wire 2]] green
|-
| 7 || 4 || tip
| [[File:Wire white brown stripe.svg|60px|Pair 4 Wire 1]] white/brown
|-
| 8 || 4 || ring
| [[File:Wire brown.svg|60px|Pair 4 Wire 2]] brown
|}

Most Ethernet cables are wired ''straight-through'' (pin 1 to pin 1, pin 2 to pin 2, and so on). In some instances, the ''[[Ethernet crossover cable|crossover]]'' form (receive to transmit and transmit to receive) may still be required.

A cable for Ethernet may be wired to either the [[ANSI/TIA-568#T568A and T568B termination|T568A or T568B]] termination standard at both ends of the cable. Since these standards differ only in that they swap the positions of pairs 2 and 3{{dash}}the only pairs used by the formerly common 10BASE-T and 100BASE-TX{{dash}}a cable with T568A wiring at one end and T568B at the other functions as a crossover cable for the older, two-pair standards.

A 10BASE-T or 100BASE-TX host normally uses connector wiring called ''[[medium dependent interface]]'' (''MDI''), transmitting on pins 1 and 2 and receiving on pins 3 and 6. An infrastructure node (such as a [[Ethernet hub|hub]] or a [[Ethernet switch|switch]]) normally uses the complementary wiring arrangement, called ''MDI-X'', the ''X'' standing for ''-crossover''. MDI-X simply reverses the pairs, transmitting on pins 3 and 6 and receiving on pins 1 and 2. These ports are connected using a [[straight-through cable]] so each transmitter talks to the receiver on the other end of the cable. (Modern twisted-pair Ethernet uses all four pairs, differently, and the MDI–MDI-X distinction does not apply.)

Later equipment often can automatically switch between MDI and MDI-X arrangements as needed, obviating crossover cables and manual selection, but in the conventional arrangement, when two nodes having the same (fixed) type of port need to be connected, a crossover cable is required. If both devices being connected support 1000BASE-T, they will connect regardless of whether a straight-through or crossover cable is used.<ref>IEEE 802.3 ''40.1.4 Signaling''</ref>

A 10BASE-T transmitter sends two [[differential signaling|differential]] voltages, +2.5&nbsp;V or −2.5&nbsp;V. A 100BASE-TX transmitter sends three differential voltages, +1&nbsp;V, 0&nbsp;V, or −1&nbsp;V.<ref>
{{cite book
|title = Electromagnetic Compatibility: principles and applications
|url = https://books.google.com/books?id=392CdZHdUDEC&pg=PA240
|author = David A. Weston |publisher= CRC Press |year= 2001
|isbn = 0-8247-8889-3 |pages= 240–242
|access-date = June 11, 2011
}}
</ref> Unlike earlier Ethernet standards using [[broadband]] and [[coaxial cable]], such as [[10BASE5]] (thicknet) and [[10BASE2]] (thinnet), 10BASE-T does not specify the exact type of wiring to be used but instead specifies certain characteristics that a cable must meet. This was done in anticipation of using 10BASE-T in existing twisted-pair wiring systems that did not conform to any specified wiring standard. Some of the specified characteristics are [[attenuation]], [[characteristic impedance]], [[propagation delay]], and several types of [[crosstalk]]. Cable testers are widely available to check these parameters to determine if a cable can be used with 10BASE-T. These characteristics are expected to be met by 100 meters of 24-[[American wire gauge|gauge]] unshielded twisted-pair cable. However, with high-quality cabling, reliable cable runs of 150 meters or longer are often achievable and are considered viable by technicians familiar with the 10BASE-T specification.{{Citation needed|date=February 2011}}

100BASE-TX follows the same wiring patterns as 10BASE-T, but is more sensitive to wire quality and length, due to the higher [[bit rate]]s.

1000BASE-T uses all four pairs bi-directionally using [[Telephone hybrid|hybrid circuits]] and [[Echo suppression and cancellation|cancellers]].<ref>IEEE 802.3 ''40.1.3 Operation of 1000BASE-T''</ref> Data is encoded using 4D-PAM5; four dimensions using [[pulse-amplitude modulation]] (PAM) with five [[voltage]]s, −2&nbsp;V, −1&nbsp;V, 0&nbsp;V, +1&nbsp;V, and +2&nbsp;V.<ref>{{cite web |url=https://grouper.ieee.org/groups/802/3/minutes/july98/E2_0798.pdf |archive-url=https://ghostarchive.org/archive/20221009/http://grouper.ieee.org/groups/802/3/minutes/july98/E2_0798.pdf |archive-date=2022-10-09 |url-status=live |author=Steve Prior |title=1000BASE-T Duffer's Guide to Basics and Startup |access-date=2011-02-18}}</ref> While +2&nbsp;V to −2&nbsp;V may appear at the pins of the line driver, the voltage on the cable is nominally +1&nbsp;V, +0.5&nbsp;V, 0&nbsp;V, −0.5&nbsp;V and −1&nbsp;V.<ref>{{cite web |url=https://www.eetimes.com/voltage-mode-line-drivers-save-on-power/ |author1=Nick van Bavel |author2=Phil Callahan |author3=John Chiang |title=Voltage-mode line drivers save on power |website=[[EE Times]] |date=2004-10-25 |access-date=2022-08-30}}</ref>

100BASE-TX and 1000BASE-T were both designed to require a minimum of [[Category 5 cable]] and also specify a maximum cable length of {{Convert|100|m||abbr=}}.

=== Shared cable ===
{{See also|Category 5 cable#Shared cable}}

10BASE-T and 100BASE-TX require only two pairs (pins 1–2, 3–6) to operate. Since common Category 5 cable has four pairs, it is possible to use the spare pairs (pins 4–5, 7–8) in 10- and 100-Mbit/s configurations for other purposes. The spare pairs may be used for [[power over Ethernet]] (PoE), for two [[plain old telephone service]] (POTS) lines, or for a second 10BASE-T or 100BASE-TX connection. In practice, great care must be taken to separate these pairs as 10/100-Mbit/s Ethernet equipment [[Electrical termination|electrically terminates]] the unused pins ("Bob Smith Termination").<ref>{{cite web|url=https://resources.altium.com/p/bob-smith-termination-it-correct-ethernet |title=Bob Smith Termination: Is it Correct for Ethernet? |last=Peterson |first=Zachariah |date=2020-10-28 |website=altium.com |access-date=2022-05-14}}</ref> Shared cable is not an option for Gigabit Ethernet as 1000BASE-T requires all four pairs to operate.

=== Single-pair{{anchor|SPE|Single-pair Ethernet}} ===
<!-- {{main|Single Pair Ethernet}} -- redirect back to this section -->
In addition to the more computer-oriented two and four-pair variants, the [[Classic Ethernet#10BASE-T1|10BASE-T1]],<ref>IEEE 802.3cg-2019 Clause 146–147</ref> [[100BASE-T1]]<ref>IEEE 802.3bw-2015 Clause 96</ref> and [[1000BASE-T1]]<ref>{{Cite web|url=http://www.ieee802.org/3/bp/ |title=IEEE P802.3bp 1000BASE-T1 PHY Task Force |publisher=IEEE 802.3 |date=2016-07-29 }}</ref> single-pair Ethernet (SPE) physical layers are intended for industrial and automotive applications<ref>{{cite web| url = https://planetechusa.com/blog/ieee-standardizes-802-3bw-ethernet-adopts-automobile-application/| title = New 802.3bw Ethernet Auto Standard Leaves LVDS Cables in the Dust| date = 8 April 2016}}</ref> or as optional data channels in other interconnect applications.<ref>IEEE 802.3bw Clause 96 and 802.3bp Clause 97</ref> The distances that single pair operates at full duplex depends on the speed: 1000m (1km) with 802.3cg-2019  10BASE-T1L; {{Convert|15|m||abbr=on|disp=or}} with 100BASE-T1 (link segment type A); up to {{Convert|40|m||abbr=on|disp=or}} using 1000BASE-T1 link segment type B with up to four in-line connectors. Both physical layers require a balanced twisted pair with an [[Impedance (electrical)|impedance]] of 100&nbsp;Ω. The cable must be capable of transmitting 600&nbsp;MHz for 1000BASE-T1 and 66&nbsp;MHz for 100BASE-T1. 2.5&nbsp;Gb/s, 5&nbsp;Gb/s, and 10&nbsp;Gb/s over a 15&nbsp;m single pair is standardized in 802.3ch-2020.<ref>{{cite web | title = IEEE Std 802.3ch-2020: Multi-Gig Automotive Ethernet PHY | url = https://blog.siemon.com/standards/ieee-p802-3ch-multi-gig-automotive-ethernet-phy | first = Valerie | last = Maguire | date = 2020-06-04 }}</ref> In June 2023, 802.3cy added 25&nbsp;Gb/s speeds at lengths up to 11&nbsp;m.<ref name="ieee802.3cy-2023">{{cite web | url = https://standards.ieee.org/ieee/802.3cy/10280/ | archive-url = https://web.archive.org/web/20220516162342/https://standards.ieee.org/ieee/802.3cy/10280/ | url-status = dead | archive-date = May 16, 2022 | title = Physical Layer Specifications and Management Parameters for 25 Gb/s - Electrical Automotive Ethernet | publisher = IEEE | date = 2023-08-11 }}</ref>

Similar to PoE, [[Power over Data Lines]] (PoDL) can provide up to 50&nbsp;W to a device.<ref>IEEE 802.3bu-2016 ''104. Power over Data Lines (PoDL) of Single Balanced Twisted-Pair Ethernet''</ref>