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Talk:Power over Ethernet

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The technology for PoE includes other components, such as Midspan power delivery, structured cabling and powered switches, and SNMP management. Merge would provide opportunity to show how the items work together without chasing all over for links. -- Kelley

The rather long quote from marvel in that section seems to make two assumptions. Firstly that all links are maximum length and secondly that all the powered devices are drawing full power. These assumptions are clearly highly unrealistic and as such real savings will be far lower. Plugwash (talk) 01:44, 25 March 2013 (UTC)[reply]

I would be for removing the quote, if there was interest in doing that. It seems to me to exaggerate in other ways, too. Gah4 (talk) 19:30, 14 September 2018 (UTC)[reply]

I have removed the quote. ~Kvng (talk) 19:52, 5 December 2021 (UTC)[reply]

I can't figure out the meaning of: Polarity is required on data pairs, and ambiguously implemented for spare pairs, with the use of a diode bridge. . While data pairs are supposed to be wired a certain way, many systems allow for polarity reversal. (It was an advertised feature on 10baseT transceivers, along with the LED to indicate wrong polarity. Device worked fine, though.) With crossover cables, and auto-MDI-X, there are lots of polarity combinations that could exist in actual wiring. Which ones are PoE devices expected to work with? This statement doesn't help explain it to me. Gah4 (talk) 19:35, 14 September 2018 (UTC)[reply]

I notice the recent change regarding this, and forgot that I asked this. It seems to me that the expectation is that you put the diode bridge on all pairs to be sure no matter what happens. The recent changes doesn't help. Gah4 (talk) 00:32, 23 June 2020 (UTC)[reply]

All of the PD implementations I've seen feature a diode bridge to sort out any polarity issues. ~Kvng (talk) 19:52, 5 December 2021 (UTC)[reply]

I think this sections needs some clarification. What does it mean for power to be trasmitted "between pairs"? To my understanding, voltage is a difference of two potentials so "no voltage present within each pair" does not make sense to me. A voltage always needs a reference point which is not given here or at least not explicitly.

Zciurus (talk) 13:54, 13 December 2021 (UTC)[reply]

See the Pinout table: endspan/mode A has DC+ on RX+/RX- and DC- on TX+/TX-. Between RX+ and RX- there's no voltage, same with TX+ and TX-. --Zac67 (talk) 16:41, 13 December 2021 (UTC)[reply]

I have reworked the sentence attempting to clarify. ~Kvng (talk) 12:42, 16 December 2021 (UTC)[reply]

Why is the pinout different on this page compared to this page? The RX and TX seem to be switched. Is one of them incorrect? Are both correct? Ralpha9 (talk) 00:16, 28 December 2021 (UTC)[reply]

At some point, both are correct as transmit and receive depend on which end you are on. MDI is the usual pinout for NIC in/on computers. MDI-X is usual for repeaters and switches meant to connect to MDI devices. One of them is labeled MDI-X. But it mostly doesn't matter now. Gigabit (1000baseT) uses all four pairs for transmit and receive, and when in 100baseTX or 10baseT mode, can figure out which one is connected to which. Normally it is straight vs. crossover, but as well as I know it, they can figure out any combination as long as the pairs are correct. Gah4 (talk) 01:19, 28 December 2021 (UTC)[reply]

I think this article needs an opening section that uses plain language to generally explain the "Why" and "How" of PoE. The name "Power over Ethernet" may be descriptive and self evident to people who are technical, but a lay person might not even be able to identify what Ethernet is. -- William Graham ^talk 02:01, 21 October 2023 (UTC)[reply]

This seems to be covered by the second sentence in the lead This allows a single cable to provide both a data connection and enough electricity to power networked devices such as wireless access points (WAPs), IP cameras and VoIP phones. ~Kvng (talk) 15:23, 4 November 2023 (UTC)[reply]