Editing Power over Ethernet (section)

==Standards development==
===Two- and four-pair Ethernet===
The original PoE standard, ''IEEE 802.3af-2003'',<ref>{{citation |title=802.3af-2003 |date=June 2003}}</ref> now known as ''Type 1'', provides up to 15.4&nbsp;W of [[Direct current|DC]] power (minimum {{nowrap|44 V DC}} and 350&nbsp;mA)<ref>IEEE 802.3-2005, section 2, table 33-5, item 1</ref><ref>IEEE 802.3-2005, section 2, table 33-5, item 4</ref> on each port.<ref>IEEE 802.3-2005, section 2, table 33-5, item 14</ref> Only 12.95&nbsp;W is guaranteed to be available at the powered device as some power dissipates in the cable.<ref>IEEE 802.3-2005, section 2, clause 33.3.5.2</ref>

The first update to PoE, ''IEEE 802.3at-2009'',<ref>{{citation |title=802.3at Amendment 3: Data Terminal Equipment (DTE) Power via the Media Dependent Interface (MDI) Enhancements |date=September 11, 2009}}</ref> introduced ''Type 2'', also known as ''PoE+'' or ''PoE&nbsp;plus''. It provides up to 25.5&nbsp;W and prohibits the use of four pairs simultaneously for power.<ref name="standards.ieee.org">{{cite web |url=http://standards.ieee.org/announcements/stdbd_approves_ieee802.3at.html |title=Amendment to IEEE 802.3 Standard Enhances Power Management and Increases Available Power |publisher=IEEE |access-date=2010-06-24 |archive-date=2012-10-16 |archive-url=https://web.archive.org/web/20121016220504/http://standards.ieee.org/news/ |url-status=dead }}</ref><ref>Clause 33.3.1 stating, "PDs that simultaneously require power from both Mode A and Mode B are specifically not allowed by this standard."</ref>

Both of these standards, 802.3af and 802.3at, were later incorporated into the [[IEEE 802.3-2012]] publication.<ref "802.3-2012">
{{cite book
|author      = <!-- not stated -->
|date        = 28 December 2012
|doi         = 10.1109/IEEESTD.2022.9844436
|title       = IEEE Std 802.3-2012 (Revision to IEEE Std 802.3-2008) – IEEE Standard for Ethernet
|url         = https://ieeexplore.ieee.org/document/6419735
|website     = IEEE Xplore
|publisher   = IEEE Standards Association
|isbn = 978-1-5044-8725-2
|access-date = 7 Jan 2025
}}
</ref>

Later ''Type 3'' and ''Type 4'' were introduced in ''IEEE 802.3bt-2018'', respectively allowing up to 51&nbsp;W and up to 71.3&nbsp;W delivered power, optionally by using all four pairs for power.<ref>Clause 33.3.1 stating, "A PD may indicate the ability to accept power on both pairsets from a Clause 145 PSE using TLV variable PD 4PID."</ref> Each pair needs to handle a current of up to 600&nbsp;[[Ampere|mA]] (Type&nbsp;3) or 960&nbsp;mA (Type&nbsp;4).<ref>IEEE 802.3bt ''145.1.3 System parameters''</ref> Additionally, power capabilities are defined for [[2.5GBASE-T and 5GBASE-T|2.5GBASE-T, 5GBASE-T]] and [[10GBASE-T]].<ref>{{cite web |url=http://www.ieee802.org/3/bt/public/jan16/hstewart_02_0116_baseline.pdf |title=IEEE P802.3bt/D1.5 Draft Standard for Ethernet – Amendment: Physical Layer and Management Parameters for DTE Power via MDI over 4-Pair |date=30 November 2015 |access-date=2017-04-09 |archive-date=2017-04-10 |archive-url=https://web.archive.org/web/20170410051052/http://www.ieee802.org/3/bt/public/jan16/hstewart_02_0116_baseline.pdf |url-status=live }}</ref> This development opens the door to new applications and expands the use of applications such as high-performance [[wireless access point]]s and surveillance cameras.

IEEE 802.3bt was incorporated into 802.3 in the 2022 revision.<ref "802.3-2022">
{{cite book
|author      = <!-- not stated -->
|date        = 29 July 2022
|doi         = 10.1109/IEEESTD.2022.9844436
|title       = IEEE Std 802.3-2022 (Revision of IEEE Std 802.3-2018) – IEEE Standard for Ethernet
|url         = https://ieeexplore.ieee.org/document/9844436
|website     = IEEE Xplore
|publisher   = IEEE Standards Association
|isbn = 978-1-5044-8725-2
|access-date = 7 Jan 2025
}}
</ref>

===Single-pair Ethernet===
The ''IEEE 802.3bu-2016''<ref>{{cite web |url=http://www.ieee802.org/3/bu/index.html |title=IEEE P802.3bu 1-Pair Power over Data Lines (PoDL) Task Force |date=2017-03-17 |access-date=2017-10-30 |archive-date=2017-10-10 |archive-url=https://web.archive.org/web/20171010063853/http://www.ieee802.org/3/bu/index.html |url-status=live }}</ref> amendment introduced ''single-pair'' ''Power over Data Lines ({{visible anchor|PoDL}})'' for the single-pair Ethernet standards [[100BASE-T1]] and [[1000BASE-T1]] intended for automotive and industrial applications.<ref>{{cite web |url=https://www.eenewsautomotive.com/news/new-automotive-power-over-ethernet-standard-extends-wattage-range |title=Automotive power-over-Ethernet standard extends wattage range |date=2017-03-13 |access-date=2021-01-16 |archive-date=2021-01-22 |archive-url=https://web.archive.org/web/20210122004440/https://www.eenewsautomotive.com/news/new-automotive-power-over-ethernet-standard-extends-wattage-range |url-status=live }}</ref> On the two-pair and four-pair standards, the power voltage is applied between one conductor of each of two pairs, so that within each pair there is no differential voltage other than that representing the transmitted data. With single-pair Ethernet, power is transmitted in parallel to the data. PoDL initially defined ten power classes, ranging from 0.5 to 50&nbsp;W (at PD).

Subsequently, PoDL was added to the single-pair variants [[Classic Ethernet#10BASE-T1|10BASE-T1]],<ref name="802.3cg">IEEE 802.3cg-2019</ref> [[2.5GBASE-T and 5GBASE-T|2.5GBASE-T1, 5GBASE-T1]], and [[10 Gigabit Ethernet#10GBASE-T1|10GBASE-T1]],<ref>IEEE 802.3ch-2020</ref> and {{asof|2021|lc=y}} it includes a total of 15 power classes with additional intermediate voltage and power levels.<ref name="802.3cg" />