Power over Ethernet

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In this configuration, an Ethernet connection includes Power over Ethernet (PoE) (gray cable looping below), and a PoE splitter provides a separate data cable (gray, looping above) and power cable (black, also looping above) for a wireless access point. The splitter is the silver and black box in the middle between the wiring junction box (left) and the access point (right). The PoE connection eliminates the need for a nearby power outlet. In another common configuration, the access point or other connected device includes internal PoE splitting and the external splitter is not necessary. ZyXEL ZyAIR G-1000 and D-Link DWL-P50 20060829 2.jpg
In this configuration, an Ethernet connection includes Power over Ethernet (PoE) (gray cable looping below), and a PoE splitter provides a separate data cable (gray, looping above) and power cable (black, also looping above) for a wireless access point. The splitter is the silver and black box in the middle between the wiring junction box (left) and the access point (right). The PoE connection eliminates the need for a nearby power outlet. In another common configuration, the access point or other connected device includes internal PoE splitting and the external splitter is not necessary.

Power over Ethernet (PoE) describes any of several standards or ad hoc systems that pass electric power along with data on twisted-pair Ethernet cabling. 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.

Contents

Techniques

There are several common techniques for transmitting power over Ethernet cabling. Three of them have been standardized by the Institute of Electrical and Electronics Engineers (IEEE) standard IEEE 802.3 since 2003.

The three techniques are:

Alternative A transmits power on the same wires as data for 10 and 100 Mbit/s Ethernet variants. This is similar to the phantom power technique commonly used for powering condenser microphones. Power is transmitted on the data conductors by applying a common voltage to each pair. Because twisted-pair Ethernet uses differential signaling, this does not interfere with data transmission. The common-mode voltage is easily extracted using the center tap of the standard Ethernet pulse transformer. For Gigabit Ethernet and faster, both alternatives A and B transmit power on wire pairs also used for data since all four pairs are used for data transmission at these speeds.

4PPoE provides power using all four pairs of a twisted-pair cable. This enables higher power for applications like pan–tilt–zoom cameras (PTZ), high-performance wireless access points (WAPs), or even charging laptop batteries.

In addition to standardizing existing practice for spare-pair (Alternative B), common-mode data pair power (Alternative A) and 4-pair transmission (4PPoE), the IEEE PoE standards provide for signaling between the power sourcing equipment (PSE) and powered device (PD). This signaling allows the presence of a conformant device to be detected by the power source and allows the device and source to negotiate the amount of power required or available while avoiding damage to non-compatible devices.

Standards development

Two- and four-pair Ethernet

The original IEEE 802.3af-2003 [1] PoE standard provides up to 15.4 W of DC power (minimum 44 V DC and 350 mA) [2] [3] on each port. [4] Only 12.95 W is assured to be available at the powered device as some power dissipates in the cable. [5]

The IEEE 802.3at-2009 [6] PoE standard, also known as PoE+ or PoE plus, provides up to 25.5 W of power for Type 2 devices. [7] The 2009 standard prohibits a powered device from using all four pairs for power. [8] Both of these standards have since been incorporated into the IEEE 802.3-2012 publication. [9]

The IEEE 802.3bt-2018 standard further expands the power capabilities of 802.3at. It is also known as PoE++ or 4PPoE. The standard introduces two additional power types: up to 51 W delivered power (Type 3) and up to 71.3 W delivered power (Type 4), optionally by using all four pairs for power. [10] Each pair of twisted pairs needs to handle a current of up to 600  mA (Type 3) or 960 mA (Type 4). [11] Additionally, support for 2.5GBASE-T, 5GBASE-T and 10GBASE-T is included. [12] This development opens the door to new applications and expands the use of applications such as high-performance wireless access points and surveillance cameras.

Single-pair Ethernet

The IEEE 802.3bu-2016 [13] amendment introduced single-pairPower over Data Lines (PoDL) for the single-pair Ethernet standards 100BASE-T1 and 1000BASE-T1 intended for automotive and industrial applications. [14] On the two-pair or four-pair standards, the same power voltage is applied to each conductor of the pair, 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 W (at PD).

Subsequently, PoDL was added to the single-pair variants 10BASE-T1, [15] 2.5GBASE-T1, 5GBASE-T1, and 10GBASE-T1 [16] and as of 2021 includes a total of 15 power classes with additional intermediate voltage and power levels. [15]

Uses

Examples of devices powered by PoE include: [17]

Terminology

Power sourcing equipment

Power sourcing equipment (PSE) are devices that provide ( source ) power on the Ethernet cable. This device may be a network switch, commonly called an endspan (IEEE 802.3af refers to it as endpoint), or an intermediary device between a non-PoE-capable switch and a PoE device, an external PoE injector, called a midspan device. [20]

Powered device

A powered device (PD) is any device powered by PoE, thus consuming energy. Examples include wireless access points, VoIP phones, and IP cameras.

Many powered devices have an auxiliary power connector for an optional external power supply. Depending on the design, some, none, or all of the device's power can be supplied from the auxiliary port, [21] [22] with the auxiliary port also sometimes acting as backup power in case PoE-supplied power fails.

Power management features and integration

Avaya ERS 5500 switch with 48 Power over Ethernet ports 5520-24-POE.JPG
Avaya ERS 5500 switch with 48 Power over Ethernet ports

Advocates of PoE expect PoE to become a global long-term DC power cabling standard and replace a multiplicity of individual AC adapters, which cannot be easily centrally managed. [23] Critics of this approach argue that PoE is inherently less efficient than AC power due to the lower voltage, and this is made worse by the thin conductors of Ethernet. Advocates of PoE, like the Ethernet Alliance, point out that quoted losses are for worst-case scenarios in terms of cable quality, length and power consumption by powered devices. [24] In any case, where the central PoE supply replaces several dedicated AC circuits, transformers and inverters, the power loss in cabling can be justifiable.

Integrating EEE and PoE

The integration of PoE with the IEEE 802.3az Energy-Efficient Ethernet (EEE) standard potentially produces additional energy savings. Pre-standard integrations of EEE and PoE (such as Marvell's EEPoE outlined in a May 2011 white paper) claim to achieve a savings upwards of 3 W per link. This saving is especially significant as higher-power devices come online. [25]

Standard implementation

Standards-based Power over Ethernet is implemented following the specifications in IEEE 802.3af-2003 (which was later incorporated as clause 33 into IEEE 802.3-2005) or the 2009 update, IEEE 802.3at. The standards require category 5 cable or better for high power levels but allow using category 3 cable if less power is required. [26]

Power is supplied as a common-mode signal over two or more of the differential pairs of wires found in the Ethernet cables and comes from a power supply within a PoE-enabled networking device such as an Ethernet switch or can be injected into a cable run with a midspan power supply, an additional PoE power source that can be used in combination with a non-PoE switch.

A phantom power technique is used to allow the powered pairs to also carry data. This permits its use not only with 10BASE-T and 100BASE-TX, which use only two of the four pairs in the cable, but also with 1000BASE-T (gigabit Ethernet), 2.5GBASE-T, 5GBASE-T, and 10GBASE-T which use all four pairs for data transmission. This is possible because all versions of Ethernet over twisted pair cable specify differential data transmission over each pair with transformer coupling; the DC supply and load connections can be made to the transformer center-taps at each end. Each pair thus operates in common mode as one side of the DC supply, so two pairs are required to complete the circuit. The polarity of the DC supply may be inverted by crossover cables; the powered device must operate with either pair: spare pairs 4–5 and 7–8 or data pairs 1–2 and 3–6. Polarity is defined by the standards on spare pairs, and ambiguously implemented for data pairs, with the use of a diode bridge.

Comparison of PoE parameters
Property802.3af (802.3at Type 1), PoE802.3at Type 2, PoE+802.3bt Type 3, 4PPoE [27] or PoE++802.3bt Type 4, 4PPoE or PoE++
Power available at PD [note 1] 12.95 W25.50 W51 W71.3 W
Maximum power delivered by PSE15.40 W30.0 W60 W90 W [28]
Voltage range (at PSE)44.0–57.0 V [29] 50.0–57.0 V [29] 52.0–57.0 V
Voltage range (at PD)37.0–57.0 V [30] 42.5–57.0 V [30] [31] 41.1–57.0 V
Maximum current Imax350 mA [32] 600 mA per pair [32] [31] 960 mA per pair [31]
Maximum cable resistance per pairset20 Ω [33] (Category 3)12.5 Ω [33] [31] (Category 5)
Power managementThree power class levels (1–3) negotiated by signatureFour power class levels (1–4) negotiated by signature or 0.1 W steps negotiated by LLDPSix power class levels (1–6) negotiated by signature or 0.1 W steps negotiated by LLDP [34] Eight power class levels (1–8) negotiated by signature or 0.1 W steps negotiated by LLDP
Derating of maximum cable ambient operating temperatureNone5 °C (9 °F) with one mode (two pairs) active10 °C (20 °F) with more than half of bundled cables pairs at Imax [35] 10 °C (20 °F) with temperature planning required
Supported cablingCategory 3 and Category 5 [26] Category 5 [26] [note 2]
Supported modesMode A (endspan), Mode B (midspan)Mode A, Mode BMode A, Mode B, 4-pair Mode4-pair Mode Mandatory

Notes:

  1. ↑ Most switched-mode power supplies within the powered device will lose another 10 to 25% of the available power to heat.
  2. ↑ More stringent cable specification allows assumption of more current carrying capacity and lower resistance (20.0 Ω for Category 3 versus 12.5 Ω for Category 5).

Powering devices

Three modes, A, B, and 4-pair are available. Mode A delivers power on the data pairs of 100BASE-TX or 10BASE-T. Mode B delivers power on the spare pairs. 4-pair delivers power on all four pairs. PoE can also be used on 1000BASE-T, 2.5GBASE-T, 5GBASE-T and 10GBASE-T Ethernet, in which case there are no spare pairs and all power is delivered using the phantom technique.

Mode A has two alternate configurations (MDI and MDI-X), using the same pairs but with different polarities. In mode A, pins 1 and 2 (pair #2 in T568B wiring) form one side of the 48 V DC, and pins 3 and 6 (pair #3 in T568B) form the other side. These are the same two pairs used for data transmission in 10BASE-T and 100BASE-TX, allowing the provision of both power and data over only two pairs in such networks. The free polarity allows PoE to accommodate crossover cables, patch cables and Auto MDI-X.

In mode B, pins 4–5 (pair #1 in both T568A and T568B) form one side of the DC supply and pins 7–8 (pair #4 in both T568A and T568B) provide the return; these are the spare pairs in 10BASE-T and 100BASE-TX. Mode B, therefore, requires a 4-pair cable.

The PSE, not the PD, decides whether power mode A or B shall be used. PDs that implement only mode A or mode B are disallowed by the standard. [36] The PSE can implement mode A or B or both. A PD indicates that it is standards-compliant by placing a 25 kΩ resistor between the powered pairs. If the PSE detects a resistance that is too high or too low (including a short circuit), no power is applied. This protects devices that do not support PoE. An optional power class feature allows the PD to indicate its power requirements by changing the sense resistance at higher voltages.

To retain power, the PD must use at least 5–10 mA for at least 60 ms at a time. If the PD goes more than 400 ms without meeting this requirement, the PSE will consider the device disconnected and, for safety reasons, remove power. [37]

There are two types of PSEs: endspans and midspans. Endspans (commonly called PoE switches) are Ethernet switches that include the power over Ethernet transmission circuitry. Midspans are power injectors that stand between a regular Ethernet switch and the powered device, injecting power without affecting the data. Endspans are normally used on new installations or when the switch has to be replaced for other reasons (such as moving from 10/100 Mbit/s to 1 Gbit/s), which makes it convenient to add the PoE capability. Midspans are used when there is no desire to replace and configure a new Ethernet switch, and only PoE needs to be added to the network.

Stages of powering up a PoE link
StageActionVolts specified (V)
802.3af802.3at
DetectionPSE detects if the PD has the correct signature resistance of 19–26.5 kΩ2.7–10.1
ClassificationPSE detects resistor indicating power range (see below)14.5–20.5
Mark 1Signals PSE is 802.3at capable. PD presents a 0.25–4 mA load.—7–10
Class 2PSE outputs classification voltage again to indicate 802.3at capability—14.5–20.5
Mark 2Signals PSE is 802.3at capable. PD presents a 0.25–4 mA load.—7–10
StartupStartup voltage [38] [39] > 42> 42
Normal operationSupply power to device [38] [39] 37–5742.5–57

IEEE 802.3at capable devices are also referred to as Type 2. An 802.3at PSE may also use LLDP communication to signal 802.3at capability. [40]

Power levels available [41] [42]
ClassUsageClassification current (mA)Power range at PD (W)Max power from PSE (W)Class description
0Default0–50.44–12.9415.4Classification unimplemented
1Optional8–130.44–3.844.00Very Low power
2Optional16–213.84–6.497.00Low power
3Optional25–316.49–12.9515.4Mid power
4Valid for Type 2 (802.3at) devices,
not allowed for 802.3af devices		35–4512.95–25.5030High power
5Valid for Type 3 (802.3bt) devices36–44 & 1–440 (4-pair)45
636–44 & 9–1251 (4-pair)60
7Valid for Type 4 (802.3bt) devices36–44 & 17–2062 (4-pair)75
836–44 & 26–3071.3 (4-pair)90

Class 4 can only be used by IEEE 802.3at (Type 2) devices, requiring valid Class 2 and Mark 2 currents for the power-up stages. An 802.3af device presenting a class 4 current is considered non-compliant and, instead, will be treated as a Class 0 device. [43] : 13 

Configuration via Ethernet layer 2 LLDP

Link Layer Discovery Protocol (LLDP) is a layer-2 Ethernet protocol for managing devices. LLDP allows an exchange of information between a PSE and a PD. This information is formatted in type–length–value (TLV) format. PoE standards define TLV structures used by PSEs and PDs to signal and negotiate available power.

LLDP Power via MDI TLV IEEE 802.3-2015 [44]
TLV HeaderTLV information string
Type  
(7 bits)		Length
(9 bits)		IEEE 802.3 OUI  
(3 octets)		IEEE 802.3 subtype
(1 octet)		MDI power support [45]
(1 octet)		PSE power pair [45]
(1 octet)		Power class 
(1 octet)		Type/source priority 
(1 octet)		PD requested power value 
(2 octets)		PSE allocated power value 
(2 octets)
1271200-12-0F2b0 port class: 1=PSE; 0=PD
b1 PSE MDI power support
b2 PSE MDI power state
b3 PSE pairs control ability
b7-4 reserved		1=signal pair
2=spare pair		1=class 0
2=class 1
3=class 2
4=class 3
5=class 4		b7 power type: 1=Type 1; 0=Type 2
b6 power type: 1=PD; 0=PSE
b5-4: power source
b3-2: reserved
b0-1 power priority: 11=low;10=high;01=critical;00=unknown		0–25.5 W in 0.1 W steps0–25.5 W in 0.1 W steps
Legacy LLDP Power via MDI TLV IEEE 802.1AB-2009 [46]
TLV HeaderTLV information string
Type  
(7 bits)		Length
(9 bits)		IEEE 802.3 OUI  
(3 octets)		IEEE 802.3 subtype
(1 octet)		MDI power support [45]
(1 octet)		PSE power pair [45]
(1 octet)		Power class 
(1 octet)
127700-12-0F2b0 port class: 1=PSE; 0=PD
b1 PSE MDI power support
b2 PSE MDI power state
b3 PSE pairs control ability
b7-4 reserved		1=signal pair
2=spare pair		1=class 0
2=class 1
3=class 2
4=class 3
5=class 4
Legacy LLDP- MED Advanced Power Management [47] : 8 
TLV Header MED HeaderExtended power via MDI
Type  
(7 bits)		Length
(9 bits)		 TIA OUI  
(3 octets)		Extended power via MDI subtype 
(1 octet)		Power type 
(2 bits)		Power source 
(2 bits)		Power priority 
(4 bits)		Power value 
(2 octets)
127700-12-BB4 PSE or PD Normal or Backup conservation Critical,
High,
Low		0–102.3 W in 0.1 W steps

The setup phases are as follows:

The rules for this power negotiation are:

Non-standard implementations

There are more than ten proprietary implementations. [48] The more common ones are discussed below.

Cisco

Some Cisco WLAN access points and VoIP phones supported a proprietary form of PoE [49] many years before there was an IEEE standard for delivering PoE. Cisco's original PoE implementation is not software upgradeable to the IEEE 802.3af standard. Cisco's original PoE equipment is capable of delivering up to 10 W per port. The amount of power to be delivered is negotiated between the endpoint and the Cisco switch based on a power value that was added to the Cisco proprietary Cisco Discovery Protocol (CDP). CDP is also responsible for dynamically communicating the Voice VLAN value from the Cisco switch to the Cisco VoIP Phone.

Under Cisco's pre-standard scheme, the PSE (switch) will send a fast link pulse (FLP) on the transmit pair. The PD (device) connects the transmit line to the receive line via a low-pass filter. The PSE gets the FLP in return. The PSE will provide a common mode current between pairs 1 and 2, resulting in 48 V DC [50] and 6.3 W [51] default of allocated power. The PD must then provide Ethernet link within 5 seconds to the auto-negotiation mode switch port. A later CDP message with a TLV tells the PSE its final power requirement. A discontinuation of link pulses shuts down power. [52]

In 2014, Cisco created another non-standard PoE implementation called Universal Power over Ethernet (UPOE). UPOE can use all 4 pairs, after negotiation, to supply up to 60 W. [53]

Analog Devices

A proprietary high-power development called LTPoE++, using a single Cat 5e Ethernet cable, is capable of supplying varying levels at 38.7, 52.7, 70, and 90 W. [54]

Microsemi

PowerDsine, acquired by Microsemi in 2007, which was then acquired by Microchip in 2018, has been selling midspan power injectors since 1999. Using Microchip's multi-PoE PSE ICs, PoE injectors and switches can support the IEEE 802.3 PoE standards and also pre-standard configurations. Several companies such as Polycom, 3Com, Lucent and Nortel used PowerDsine's older Power over LAN PoE implementation. [55]

Passive

In a passive PoE system, the injector does not communicate with the powered device to negotiate its voltage or wattage requirements but merely supplies power at all times. Common 100 Mbit/s passive applications use the pinout of 802.3af mode B (see § Pinouts) –with DC positive on pins 4 and 5 and DC negative on 7 and 8 and data on 1–2 and 3–6, but polarization may vary. Gigabit passive injectors use a transformer on the data pins to allow power and data to share the cable and are typically compatible with 802.3af Mode A. Passive midspan injectors with up to 12 ports are available.

Devices needing 5 volts cannot typically use PoE at 5 V on Ethernet cable beyond short distances (about 15 feet (4.6 m)) as the voltage drop of the cable becomes too significant, so a 24 V or 48 V to 5 V DC-DC converter is required at the remote end. [56] [ unreliable source? ]

Passive PoE power sources are commonly used with a variety of indoor and outdoor wireless radio equipment, most commonly from Motorola (now Cambium), Ubiquiti Networks, MikroTik and others. Earlier versions of passive PoE 24 VDC power sources shipped with 802.11a, 802.11g and 802.11n-based radios are commonly 100 Mbit/s only.

Passive DC-to-DC injectors also exist which convert a 9 V to 36 V DC, or 36 V to 72 V DC power source to a stabilized 24 V 1 A, 48 V 0.5 A, or up to 48 V 2.0 A PoE feed with '+' on pins 4 & 5 and '−' on pins 7 & 8. These DC-to-DC PoE injectors are used in various telecom applications. [57]

Power capacity limits

The ISO/IEC TR 29125 and Cenelec EN 50174-99-1 draft standards outline the cable bundle temperature rise that can be expected from the use of 4PPoE. A distinction is made between two scenarios:

  1. bundles heating up from the inside to the outside, and
  2. bundles heating up from the outside to match the ambient temperature.

The second scenario largely depends on the environment and installation, whereas the first is solely influenced by the cable construction. In a standard unshielded cable, the PoE-related temperature rise increases by a factor of 5. In a shielded cable, this value drops to between 2.5 and 3, depending on the design.

Pinouts

802.3af/at/bt standards A and B from the power sourcing equipment perspective (MDI-X)
Pins at switchT568A colorT568B color10/100 mode B,
DC on spares		10/100 mode A,
mixed DC & data		1000 (1 gigabit) mode B,
DC & bi-data		1000 (1 gigabit) mode A,
DC & bi-data		1000 (1 gigabit) mode A+B (4PPoE),
DC & bi-data [note 1]
Pin 1 Wire white green stripe.svg
White/green stripe		 Wire white orange stripe.svg
White/orange stripe		Rx +Rx +DC +TxRx A +TxRx A +DC +TxRx A +DC +
Pin 2 Wire green.svg
Green solid		 Wire orange.svg
Orange solid		Rx −Rx −DC +TxRx A −TxRx A −DC +TxRx A −DC +
Pin 3 Wire white orange stripe.svg
White/orange stripe		 Wire white green stripe.svg
White/green stripe		Tx +Tx +DC −TxRx B +TxRx B +DC −TxRx B +DC −
Pin 4 Wire blue.svg
Blue solid		DC +UnusedTxRx C +DC +TxRx C +TxRx C +DC +
Pin 5 Wire white blue stripe.svg
White/blue stripe		DC +TxRx C −DC +TxRx C −TxRx C −DC +
Pin 6 Wire orange.svg
Orange solid		 Wire green.svg
Green solid		Tx −Tx −DC −TxRx B −TxRx B −DC −TxRx B −DC −
Pin 7 Wire white brown stripe.svg
White/brown stripe		DC −UnusedTxRx D +DC −TxRx D +TxRx D +DC −
Pin 8 Wire brown.svg
Brown solid		DC −TxRx D −DC −TxRx D −TxRx D −DC −
Notes:
  1. ↑ Only supported by 802.3bt for devices that identify as the newly added Type 3 or Type 4. [note 2]
  2. IEEE 802.3bt-2018, clause 145.2.9 stating "A PSE shall not apply 4-pair power unless the PSE [...] has identified the PD as Type 3 or Type 4."

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The OPEN Alliance is a non-profit, special interest group (SIG) of mainly automotive industry and technology providers collaborating to encourage wide scale adoption of Ethernet-based communication as the standard in automotive networking applications.

IEEE 802.3bz, NBASE-T and MGBASE-T are standards released in 2016 for Ethernet over twisted pair at speeds of 2.5 and 5 Gbit/s. These use the same cabling as the ubiquitous Gigabit Ethernet, yet offer higher speeds. The resulting standards are named 2.5GBASE-T and 5GBASE-T.

<span class="mw-page-title-main">Fibre to the office</span>

Fiber to the office (FTTO) is an alternative cabling concept for local area network (LAN) network office environments. It combines passive elements and active mini-switches to provide end devices with Gigabit Ethernet. FTTO involves centralised optical fibre cabling techniques to create a combined backbone/horizontal channel; this channel is provided from the work areas to the centralised cross-connect or interconnect by allowing the use of pull-through cables or splices in the telecommunications room.

References

  1. ↑ 802.3af-2003, June 2003
  2. ↑ IEEE 802.3-2005, section 2, table 33-5, item 1
  3. ↑ IEEE 802.3-2005, section 2, table 33-5, item 4
  4. ↑ IEEE 802.3-2005, section 2, table 33-5, item 14
  5. ↑ IEEE 802.3-2005, section 2, clause 33.3.5.2
  6. ↑ 802.3at Amendment 3: Data Terminal Equipment (DTE) Power via the Media Dependent Interface (MDI) Enhancements, September 11, 2009
  7. ↑ "Amendment to IEEE 802.3 Standard Enhances Power Management and Increases Available Power". IEEE. Archived from the original on 2012-10-16. Retrieved 2010-06-24.
  8. ↑ Clause 33.3.1 stating, "PDs that simultaneously require power from both Mode A and Mode B are specifically not allowed by this standard."
  9. ↑ IEEE 802.3-2012 Standard for Ethernet, IEEE Standards Association, December 28, 2012
  10. ↑ 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."
  11. ↑ IEEE 802.3bt 145.1.3 System parameters
  12. ↑ "IEEE P802.3bt/D1.5 Draft Standard for Ethernet – Amendment: Physical Layer and Management Parameters for DTE Power via MDI over 4-Pair" (PDF). 30 November 2015. Archived (PDF) from the original on 2017-04-10. Retrieved 2017-04-09.
  13. ↑ "IEEE P802.3bu 1-Pair Power over Data Lines (PoDL) Task Force". 2017-03-17. Archived from the original on 2017-10-10. Retrieved 2017-10-30.
  14. ↑ "Automotive power-over-Ethernet standard extends wattage range". 2017-03-13. Archived from the original on 2021-01-22. Retrieved 2021-01-16.
  15. 1 2 IEEE 802.3cg-2019
  16. ↑ IEEE 802.3ch-2020
  17. ↑ "Power over Ethernet". Commercial web page. GarrettCom. Archived from the original on August 29, 2011. Retrieved August 6, 2011.
  18. ↑ Makdessian, Alec M. "The Bright New Outlook For LEDs: New Drivers, New Possibilities" (PDF). Maxim Integrated . Archived (PDF) from the original on 8 December 2022. Retrieved 17 February 2024.
  19. ↑ "Ethernet Extender for POE and POE Plus equipment". Archived from the original on 2015-09-30. Retrieved 2015-10-26.
  20. ↑ Cisco Aironet technotes on 1000BASE-T mid-span devices, Archived 2011-08-02 at the Wayback Machine visited 18 July 2011
  21. ↑ IEEE 802.3-2008, section 2, clause 33.3.5
  22. ↑ IEEE 802.3at-2009, clause 33.3.7
  23. ↑ Dave Dwelley (Oct 26, 2003), "Banish Those "Wall Warts" With Power Over Ethernet", Electronic Design, archived from the original on 2017-11-26, retrieved 2018-07-21
  24. ↑ David Tremblay; Lennart Yseboodt (November 10, 2017), "Clarifying misperceptions about Power over Ethernet and cable losses", Cabling Installation and Maintenance, archived from the original on 2018-07-22, retrieved 2018-07-21
  25. ↑ Roman Kleinerman; Daniel Feldman (May 2011), Power over Ethernet (PoE): An Energy-Efficient Alternative (PDF), Marvell, archived (PDF) from the original on 2016-04-16, retrieved 2016-08-31
  26. 1 2 3 IEEE 802.3at-2009, clause 33.1.1c
  27. ↑ Koussalya Balasubramanian; David Abramson (May 2014). "Base Line Text for IEEE 802.3 BT" (PDF). Archived (PDF) from the original on 2017-04-02. Retrieved 2017-04-02.
  28. ↑ Overview of 802.3bt - Power over Ethernet standard (PDF), Ethernet Alliance , retrieved 2024-08-19
  29. 1 2 IEEE 802.3at-2009 Table 33-11
  30. 1 2 IEEE 802.3at-2009 Table 33-18
  31. 1 2 3 4 IEEE 802.3bt Table 145-1
  32. 1 2 IEEE 802.3at-2009 Table 33-1
  33. 1 2 IEEE 802.3at-2009 33.1.4 Type 1 and Type 2 system parameters
  34. ↑ IEEE 802.3bt 145.3.1 PD Type definitions
  35. ↑ IEEE 802.3bt 145.1.3.1 Cabling requirements
  36. ↑ IEEE 802.3 33.3.1 PD PI
  37. ↑ Herbold, Jacob; Dwelley, Dave (27 October 2003), "Banish Those "Wall Warts" With Power Over Ethernet", Electronic Design, 51 (24): 61, archived from the original on 2005-03-20
  38. 1 2 IEEE 802.3-2008, section 2, table 33-12
  39. 1 2 IEEE 802.3at-2009, table 33-18
  40. ↑ "LTC4278 IEEE 802.3at PD with Synchronous No-Opto Flyback Controller and 12V Aux Support" (PDF). cds.linear.com. p. 15. Archived from the original (PDF) on 2011-07-13.
  41. ↑ IEEE 802.3-2018, section 2, table 33-9
  42. ↑ IEEE 802.3bt, table 145-26
  43. ↑ IEEE 802.3-2008, section 2, clause 33.3.4
  44. ↑ IEEE 802.3 Clause 79.3.2 Power Via MDI TLV
  45. 1 2 3 4 IETF RFC   3621
  46. ↑ IEEE 802.1AB-2009 Annex F.3 Power Via MDI TLV
  47. 1 2 "LLDP / LLDP-MED Proposal for PoE Plus (2006-09-15)" (PDF). Archived (PDF) from the original on 2010-09-23. Retrieved 2010-01-10.2010-01-10
  48. ↑ "Power over Ethernet (POE) proprietary pinouts".
  49. ↑ "Power over Ethernet (POE) pinout". Archived from the original on 2015-04-01.
  50. ↑ "Planning for Cisco IP Telephony > Network Infrastructure Analysis". Archived from the original on 2011-07-08. Retrieved 2010-01-12. 2010-01-12 ciscopress.com
  51. ↑ "Power over Ethernet on the Cisco Catalyst 6500 Series Switch" (PDF). Archived from the original (PDF) on 2010-11-06. 2010-01-12 conticomp.com
  52. ↑ "Understanding the Cisco IP Phone 10/100 Ethernet In-Line Power Detection Algorithm - Cisco Systems". Archived from the original on 2009-02-02. Retrieved 2010-01-12. 2010-01-12 cisco.com
  53. ↑ "Cisco Universal Power Over Ethernet - Unleash the Power of your Network White Paper". Cisco Systems. 2014-07-11. Archived from the original on 2017-11-28.
  54. ↑ "Power over Ethernet Interface Controllers". Archived from the original on 2016-07-20. Retrieved 2016-07-27.
  55. ↑ PowerDsine Limited, archived from the original on 2012-07-28
  56. ↑ "5 volt power over ethernet adapters". Archived from the original on 2013-07-02.
  57. ↑ "Passive Power over Ethernet equipment, AC-DC and DC-DC". Archived from the original on 2010-06-20.
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