Template:Short description Template:Redirect Template:Redirect2 Template:Distinguish Template:Use American English
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.
TechniquesEdit
There are several common techniques for transmitting power over Ethernet cabling, defined within the broader Institute of Electrical and Electronics Engineers (IEEE) 802.3 standard since 2003.
The three techniques are:
- Alternative A, which uses the same two of the four signal pairs that 10BASE-T and 100BASE-TX use for data in typical Cat 5 cabling.
- Alternative B, which separates the data and the power conductors for 10BASE-T/100BASE-TX, making troubleshooting easier.
- 4PPoE, which uses all four twisted pairs in parallel, increasing the achievable power.
Alternative A transmits power on the same wires as data for common 10 and Template:Nowrap 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 the connectors used for twisted-pair Ethernet. 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 common-mode data pair (Alternative A), spare-pair (Alternative B), and four-pair (4PPoE) transmission, 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 developmentEdit
Two- and four-pair EthernetEdit
The original PoE standard, IEEE 802.3af-2003,<ref>Template:Citation</ref> now known as Type 1, provides up to 15.4 W of DC power (minimum Template:Nowrap and 350 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 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>Template:Citation</ref> introduced Type 2, also known as PoE+ or PoE plus. It provides up to 25.5 W and prohibits the use of four pairs simultaneously for power.<ref name="standards.ieee.org">{{#invoke:citation/CS1|citation |CitationClass=web }}</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"> Template:Cite book </ref>
Later Type 3 and Type 4 were introduced in IEEE 802.3bt-2018, respectively allowing up to 51 W and up to 71.3 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 mA (Type 3) or 960 mA (Type 4).<ref>IEEE 802.3bt 145.1.3 System parameters</ref> Additionally, power capabilities are defined for 2.5GBASE-T, 5GBASE-T and 10GBASE-T.<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> This development opens the door to new applications and expands the use of applications such as high-performance wireless access points and surveillance cameras.
IEEE 802.3bt was incorporated into 802.3 in the 2022 revision.<ref "802.3-2022"> Template:Cite book </ref>
Single-pair EthernetEdit
The IEEE 802.3bu-2016<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> amendment introduced single-pair Power over Data Lines (Template:Visible anchor) for the single-pair Ethernet standards 100BASE-T1 and 1000BASE-T1 intended for automotive and industrial applications.<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</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 W (at PD).
Subsequently, PoDL was added to the single-pair variants 10BASE-T1,<ref name="802.3cg">IEEE 802.3cg-2019</ref> 2.5GBASE-T1, 5GBASE-T1, and 10GBASE-T1,<ref>IEEE 802.3ch-2020</ref> and Template:Asof it includes a total of 15 power classes with additional intermediate voltage and power levels.<ref name="802.3cg" />
UsesEdit
{{#invoke:Gallery|gallery}}
Examples of devices powered by PoE include:<ref name="PoE enabled devices">{{#invoke:citation/CS1|citation |CitationClass=web }}</ref>
- VoIP phones
- IP cameras, including PTZs
- WAPs
- IPTV decoders
- Network routers
- A small network switch, providing a small number of Ethernet ports from one uplink cable. Such a switch may in turn pass PoE to downstream devices (termed PoE pass-through).
- Intercom and public address systems
- Wall clocks, with time set using Network Time Protocol (NTP)
- Roof-mounted radios with integrated antennas, 4G/LTE-, 802.11- or 802.16-based systems used by wireless ISPs
- Outdoor point-to-point microwave and millimeter-wave radios and some free space optics units, usually using non-standard, proprietary PoE
- Industrial control system components including sensors, controllers, meters etc.
- Access control components including help points, intercoms, keyless entry, etc.
- Lighting controllers and light-emitting diode (LED) lighting fixtures<ref name="POE LED Lighting">{{#invoke:citation/CS1|citation
|CitationClass=web }}</ref>
- Stage and theatrical devices, such as networked audio breakout and routing boxes
- Remote point-of-sale (POS) kiosks
- Ethernet repeaters, or extenders, which may also pass PoE through to downstream devices<ref>{{#invoke:citation/CS1|citation
|CitationClass=web }}</ref>
- PoE splitters that output the power in a different form (e.g. USB Power Delivery), to power a remote device or charge a mobile phone
TerminologyEdit
Power sourcing equipmentEdit
802.3 refers to Power Sourcing Equipment (PSE), which provides power on the Ethernet cable. This device may be a network switch, in the standard Endpoint PSE (commonly called an endspan device) or a PoE injector, Midspan PSE in the standard, an intermediary device between a switch that does not provide PoE (or one that cannot provide sufficient power) and a PoE-powered device.<ref>Cisco Aironet technotes on 1000BASE-T Midspan PSE, Template:Webarchive visited 18 July 2011</ref>
Powered deviceEdit
802.3 refers to any PoE-powered piece of equipment as a Powered Device (PD). 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,<ref name="802.3-2008, 33.3.5 PD Power">IEEE 802.3-2008, section 2, clause 33.3.5</ref><ref name="802.3at-2009, 33.3.7 PD Power">IEEE 802.3at-2009, clause 33.3.7</ref> with the auxiliary port also sometimes providing backup power in case PoE-supplied power fails.
Power management features and integrationEdit
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.<ref>Template:Citation</ref> 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.<ref>Template:Citation</ref> 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 PoEEdit
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.<ref name="marvell1">Template:Citation</ref>
Standard implementationEdit
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.<ref name="33.1.1c">IEEE 802.3at-2009, clause 33.1.1c</ref>
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-providing networking device, such as an Ethernet switch, or by a PoE injector, a 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: the spare pairs on pins 4 and 5, and 7 and 8, or the data pairs on pins 1 and 2, and 3 and 6. Polarity is defined by the standards on spare pairs, and ambiguously implemented for data pairs, with the use of a diode bridge.
| Official name in IEEE 802.3 |
Type 1 | Type 2 | Type 3 | Type 4 | |
|---|---|---|---|---|---|
| Common name(s) | PoE | PoE+ | PoE++ / 4PPoE<ref name="802.3bt_0514">{{#invoke:citation/CS1|citation | CitationClass=web
}}</ref> | |
| Defining IEEE document | 802.3af | 802.3at | 802.3bt | ||
| Power available at PD<ref group=note>Most switched-mode power supplies within the powered device will lose another 10 to 25% of the available power to heat.</ref> | Template:Nowrap | Template:Nowrap | Template:Nowrap | Template:Nowrap | |
| Maximum power delivered by PSE | Template:Nowrap | Template:Nowrap | Template:Nowrap | Template:Nowrap<ref>Template:Citation</ref> | |
| Voltage range (at PSE) | Template:Nowrap<ref name="Table 33.11">IEEE 802.3at-2009 Table 33-11</ref> | Template:Nowrap<ref name="Table 33.11"/> | Template:Nowrap | ||
| Voltage range (at PD) | Template:Nowrap<ref name="Table 33.18">IEEE 802.3at-2009 Table 33-18</ref> | Template:Nowrap<ref name="Table 33.18"/><ref name="Table 145-1">IEEE 802.3bt Table 145-1</ref> | Template:Nowrap | ||
| Maximum current Imax | Template:Nowrap<ref name="table 33-1">IEEE 802.3at-2009 Table 33-1</ref> | Template:Nowrap per pair<ref name="table 33-1"/><ref name="Table 145-1" /> | Template:Nowrap per pair<ref name="Table 145-1" /> | ||
| Maximum cable resistance per pairset | Template:Nowrap<ref name="33.1.4">IEEE 802.3at-2009 33.1.4 Type 1 and Type 2 system parameters</ref> (Category 3) | Template:Nowrap<ref name="33.1.4" /><ref name="Table 145-1" /> (Category 5) | |||
| Power management | Three power classes Template:Nowrap negotiated by signature | Four power classes Template:Nowrap negotiated by signature or Template:Nowrap steps negotiated by LLDP | Six power classes Template:Nowrap negotiated by signature or Template:Nowrap steps negotiated by LLDP<ref>IEEE 802.3bt 145.3.1 PD Type definitions</ref> | Eight power classes Template:Nowrap negotiated by signature or Template:Nowrap steps negotiated by LLDP | |
| Derating of cable maximum ambient operating temperature | None | Template:Convert with only two pairs active, at Imax | Template:Convert with all of the bundled cables pairs active, at Imax<ref name="bt_temp">IEEE 802.3bt 145.1.3.1 Cabling requirements</ref> | Template:Convert with temperature planning required | |
| Supported cabling | Category 3 and Category 5<ref name="33.1.1c"/> | Category 5<ref name="33.1.1c"/><ref group=note>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).</ref> | |||
| Supported modes | Mode A (from Endpoint PSE), Mode B (from Midspan PSE) | Mode A, Mode B | Mode A, Mode B, 4-pair mode | 4-pair mode mandatory | |
Notes: <references group=note/>
Powering devicesEdit
Three modes, Mode A, Mode B, and 4-pair mode, are available. (In the standard these are discussed as two Modes, with the term 4-pair mode for both simultaneously.) Mode A delivers power on T568A and T568B pairs 2 and 3Template:Dashthe data pairs of 100BASE-TX or 10BASE-T. Mode B delivers power on pairs 1 and 4Template:Dashthe pairs not used by 100BASE-TX or 10BASE-T. 4-pair mode delivers power using all four pairs. PoE can also be used with 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 alternative configurations (MDI and MDI-X), using the same pairs but with different polarities. In Mode A, pins 1 and 2 (pair 3 in T568A wiring, pair 2 in T568B) form one side of the 48 V DC, and pins 3 and 6 (pair 2 in T568A, 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 pairs 10BASE-T and 100BASE-TX do not use. Mode B, therefore, requires that all four pairs of the connectors be wired.
The Power Sourcing Equipment (PSE), not the Powered Device (PD), decides whether Mode A or Mode B shall be used. PDs that implement only Mode A or Mode B are disallowed by the standard.<ref>IEEE 802.3 33.3.1 PD PI</ref> The PSE can implement Mode A, Mode B, or both (4-pair mode). 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.<ref>Template:Citation</ref>
There are two types of PSE: Endpoint and Midspan. Endpoint devices (commonly PoE switches) are Ethernet networking equipment that includes the power-over-Ethernet transmission circuitry. Midspan devices are power injectors that stand between a non-PoE Ethernet switch (or one that cannot provide sufficient power) and the powered device, injecting power without affecting the data. Endpoint devices are normally used in new installations or where the switch has to be replaced for other reasons (such as moving from Template:Nowrap to Template:Nowrap), which makes it convenient to add the PoE capability. Midspan PSE can be used e.g. to power a single piece of equipment added to a network that does not provide PoE.
| Stage | Action | Volts specified (V) | |
|---|---|---|---|
| 802.3af | 802.3at | ||
| Detection | PSE detects if the PD has the correct signature resistance of Template:Nowrap. | Template:Nowrap | |
| Classification | PSE detects resistor indicating power range (see below). | Template:Nowrap | |
| Template:Nowrap | PD signals it is 802.3at-capable. PD presents a Template:Nowrap load. | — | Template:Nowrap |
| Template:Nowrap | PSE outputs classification voltage again to indicate 802.3at capability. | — | Template:Nowrap |
| Template:Nowrap | PD signals it is 802.3at-capable. PD presents a Template:Nowrap load. | — | Template:Nowrap |
| Startup | PSE supplies startup voltage.<ref name="802.3-2008, section 2, table 33-12">IEEE 802.3-2008, section 2, table 33-12</ref><ref name="802.3at, table 33-18">IEEE 802.3at-2009, table 33-18</ref> | Template:Nowrap | Template:Nowrap |
| Normal operation | PSE supplies power to device.<ref name="802.3-2008, section 2, table 33-12"/><ref name="802.3at, table 33-18"/> | Template:Nowrap | Template:Nowrap |
IEEE 802.3at-capable devices are also referred to as Type 2. 802.3at PSE may also use LLDP communication to signal 802.3at capability.<ref name="linear-LTC4278_ds">{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> Template:Anchor
| Class | Usage | Classification current (mA) | Power range at PD (W) | Max power from PSE (W) | Class description |
|---|---|---|---|---|---|
| 0 | Default | 0–5 | 0.44–12.94 | 15.4 | Classification unimplemented |
| 1 | Optional | 8–13 | 0.44–3.84 | 4.00 | Very Low power |
| 2 | Optional | 16–21 | 3.84–6.49 | 7.00 | Low power |
| 3 | Optional | 25–31 | 6.49–12.95 | 15.4 | Mid power |
| 4 | Valid for Type 2 (802.3at) devices, not allowed for 802.3af devices |
35–45 | 12.95–25.50 | 30 | High power |
| 5 | Valid for Type 3 (802.3bt) devices | 36–44 & 1–4 | 40 (4-pair) | 45 | |
| 6 | 36–44 & 9–12 | 51 (4-pair) | 60 | ||
| 7 | Valid for Type 4 (802.3bt) devices | 36–44 & 17–20 | 62 (4-pair) | 75 | |
| 8 | 36–44 & 26–30 | 71.3 (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 non-compliant and, instead, will be treated as a Class 0 device.<ref name="802.3, section 2, 33.3.4">IEEE 802.3-2008, section 2, clause 33.3.4</ref>Template:Rp
Configuration via Ethernet LLDPEdit
Link Layer Discovery Protocol (LLDP) is a layer-2 Ethernet protocol for managing devices. LLDP allows an exchange of information between PSE and a PD. This information is formatted in type–length–value (TLV) format. PoE standards define TLV structures used by PSE and PDs to signal and negotiate available power.
| TLV Header | TLV information string | ||||||||
|---|---|---|---|---|---|---|---|---|---|
| Type (Template:Nowrap) |
Length (Template:Nowrap) |
IEEE 802.3 OUI (Template:Nowrap) |
IEEE 802.3 subtype (Template:Nowrap) |
MDI power support<ref name="RFC3621">IETF Template:IETF RFC</ref> (Template:Nowrap) |
PSE power pair<ref name="RFC3621" /> (Template:Nowrap) |
Power class (Template:Nowrap) |
Type/source priority (Template:Nowrap) |
PD-requested power value (Template:Nowrap) |
PSE-allocated power value (Template:Nowrap) |
| 127 | 12 | 00-12-0F | 2 | Bit 0: port class (1: PSE; 0: PD) Bit 1: PSE MDI power support Bit 2: PSE MDI power state Bit 3: PSE pairs control ability Bits 4–7: reserved |
1: signal pair 2: spare pair |
1: Class 0 2: Class 1 3: Class 2 4: Class 3 5: Class 4 |
Bit 7: power type (1: Type 1; 0: Type 2) Bit 6: power type (1: PD; 0: PSE) Bits 5–4: power source Bits 3–2: reserved Bits 0–1 power priority (11: low; 10: high; 01: critical; 00: unknown) |
Template:Nowrap in Template:Nowrap steps | Template:Nowrap in Template:Nowrap steps |
| TLV Header | TLV information string | |||||
|---|---|---|---|---|---|---|
| Type (Template:Nowrap) |
Length (Template:Nowrap) |
IEEE 802.3 OUI (Template:Nowrap) |
IEEE 802.3 subtype (Template:Nowrap) |
MDI power support<ref name="RFC3621">IETF Template:IETF RFC</ref> (Template:Nowrap) |
PSE power pair<ref name="RFC3621" /> (Template:Nowrap) |
Power class (Template:Nowrap) |
| 127 | 7 | 00-12-0F | 2 | Bit 0: port class (1: PSE; 0: PD) Bit 1: PSE MDI power support Bit 2: PSE MDI power state Bit 3: PSE pairs control ability Bits 7–4: reserved |
1: signal pair 2: spare pair |
1: class 0 2: class 1 3: class 2 4: class 3 5: class 4 |
| CitationClass=web
}}2010-01-10</ref>Template:Rp |
TLV Header | MED Header | Extended power via MDI | |||||
|---|---|---|---|---|---|---|---|---|
| Type (Template:Nowrap) |
Length (Template:Nowrap) |
TIA OUI (Template:Nowrap) |
Extended power via MDI subtype (Template:Nowrap) |
Power type (Template:Nowrap) |
Power source (Template:Nowrap) |
Power priority (Template:Nowrap) |
Power value (Template:Nowrap) | |
| 127 | 7 | 00-12-BB | 4 | PSE or PD | Normal or Backup conservation | Critical, High, Low |
Template:Nowrap in Template:Nowrap steps | |
The setup phases are as follows:
- The PSE (provider) tests the PD (consumer) physically using 802.3af phase class 3.
- The PSE provides baseline power to the PD.
- The PD signals to the PSE that it as a PoE PD, indicating its maximum power and requested power.
- The PSE signals to PD that it is PoE PSE, indicating the power allotted to the PD, at which point the PD can begin consuming up to the allotted power.
The rules for this power negotiation are:
- The PD shall never request more power than the physical 802.3af class.
- The PD shall never draw more than the maximum power advertised by the PSE.
- The PSE may deny any PD drawing more power than maximum it has allowed.
- The PSE shall not reduce power allocated to the PD that is in use.
- The PSE may request reduced power, via conservation mode.<ref name="ieee802-lldp-med-prop2006" />Template:Rp
Non-standard implementationsEdit
There are more than ten proprietary implementations.<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> The more common ones are discussed below.
CiscoEdit
Some Cisco WLAN access points and VoIP phones supported a proprietary form of PoE<ref name="pinout">{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> 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 Template:Nowrap 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 Template:Nowrap<ref name="ciscopress_ciscophone">{{#invoke:citation/CS1|citation |CitationClass=web }} 2010-01-12 ciscopress.com</ref> and Template:Nowrap<ref name="conticomp_CAT6500POE_ds">{{#invoke:citation/CS1|citation |CitationClass=web }} 2010-01-12 conticomp.com</ref> default of allocated power. The PD must then provide Ethernet link within Template:Nowrap 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.<ref name="cisco_technote00">{{#invoke:citation/CS1|citation |CitationClass=web }} 2010-01-12 cisco.com</ref>
Template:AnchorIn 2014, Cisco created another non-standard PoE implementation called Template:Vanchor (UPOE). UPOE can use all four pairs, after negotiation, to supply up to 60 W.<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref>
Template:AnchorAnalog DevicesEdit
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.<ref name="www.linear.com">{{#invoke:citation/CS1|citation |CitationClass=web }}</ref>
MicrosemiEdit
PowerDsine, acquired by Microsemi in 2007, which was then acquired by Microchip in 2018, has been selling 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.<ref>Template:Citation</ref>
PassiveEdit
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 Template:Nowrap passive applications use the pinout of 802.3af mode B (see Template:Section link)Template:Sndwith DC positive on pins 4 and 5 and negative on 7 and 8, and data on 1 and 2, and 3 and 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 injectors with up to 12 ports are available.
Commodity passive PoE devices often include down regulation for adding PoE to existing systems operating at 5 volts.<ref name="Active 5v Splitter manufacturer">{{#invoke:citation/CS1|citation |CitationClass=web }}</ref>Template: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 Template:Nowrap 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.<ref name="Passive PoE injector manufacturer">{{#invoke:citation/CS1|citation |CitationClass=web }}</ref>
Power capacity limitsEdit
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:
- bundles heating up from the inside to the outside, and
- 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.
PinoutsEdit
| Pins at switch | T568A color | T568B color | 10/100 mode B, DC on spares |
10/100 mode A, mixed DC & data |
1000 (1 Gbit/s) mode B, DC & bi-data |
1000 (1 Gbit/s) mode A, DC & bi-data |
1000 (1 Gbit/s) mode A+B (4PPoE), DC & bi-dataTemplate:Notetag | |||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Pin 1 | File:Wire white green stripe.svg White/green stripe |
File:Wire white orange stripe.svg White/orange stripe |
Rx + | Rx + | DC + | TxRx A + | TxRx A + | DC + | TxRx A + | DC + | ||
| Pin 2 | File:Wire green.svg Green solid |
File:Wire orange.svg Orange solid |
Rx − | Rx − | DC + | TxRx A − | TxRx A − | DC + | TxRx A − | DC + | ||
| Pin 3 | File:Wire white orange stripe.svg White/orange stripe |
File:Wire white green stripe.svg White/green stripe |
Tx + | Tx + | DC − | TxRx B + | TxRx B + | DC − | TxRx B + | DC − | ||
| Pin 4 | File:Wire blue.svg Blue solid |
DC + | colspan=2 rowspan=2 Template:N/a | TxRx C + | DC + | TxRx C + | TxRx C + | DC + | ||||
| Pin 5 | File:Wire white blue stripe.svg White/blue stripe |
DC + | TxRx C − | DC + | TxRx C − | TxRx C − | DC + | |||||
| Pin 6 | File:Wire orange.svg Orange solid |
File:Wire green.svg Green solid |
Tx − | Tx − | DC − | TxRx B − | TxRx B − | DC − | TxRx B − | DC − | ||
| Pin 7 | File:Wire white brown stripe.svg White/brown stripe |
DC − | colspan=2 rowspan=2 Template:N/a | TxRx D + | DC − | TxRx D + | TxRx D + | DC − | ||||
| Pin 8 | File:Wire brown.svg Brown solid |
DC − | TxRx D − | DC − | TxRx D − | TxRx D − | DC − | |||||
| Notes: Template:Notefoot | ||||||||||||
