Power over Ethernetwikipedia
power over EthernetPoE802.3at802.3afPower over Data Lines (PoDL)MDI powerPoE+Power-over-Ethernet

Category 5 cable

CAT5category 5 cableCategory 5
For 10BASE-T and 100BASE-TX, only two of the four signal pairs in typical Cat 5 cable are used. The IEEE standards for PoE require category 5 cable or better for high power levels but allow using category 3 cable if less power is required.
Through the use of power over Ethernet (PoE), power can be carried over the cable in addition to Ethernet data.

2.5GBASE-T and 5GBASE-T

2.5GBASE-T2.5GBASE-T and 5GBASE-T5GBASE-T
The upcoming IEEE 802.3bt standard slated for fall 2018 will introduce two additional power types: up to 55 W (Type 3) and up to 90-100 W (Type 4). Each pair of twisted pairs will need to handle a current of up to 600 mA (Type 3) or 960 mA (Type 4). Additionally, support for 2.5GBASE-T, 5GBASE-T and 10GBASE-T is planned.
Unlike the preceding 10GBASE-T standard, equipment manufacturers have indicated their intention to implement 802.3at type Power over Ethernet on certain types of NBASE-T switches.

IEEE 802.3

802.3802.3 working groupIEEE 802.3
Two of them have been standardized by IEEE 802.3 since 2003.

Network switch

network switchswitchesswitch
Power is supplied in common mode 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.
A modern switch may implement power over Ethernet (PoE), which avoids the need for attached devices, such as a VoIP phone or wireless access point, to have a separate power supply.

VoIP phone

IP PhoneIP phonesEthernet-based phone
This allows a single cable to provide both data connection and electric power to devices such as wireless access points, IP cameras, and VoIP phones.

Ethernet over twisted pair

10BASE-T10BaseT10/100/1000
Power over Ethernet or PoE describes any of several standard or ad-hoc systems which pass electric power along with data on twisted pair Ethernet cabling.
The spare pairs may be used for Power over Ethernet (PoE), or two phone lines, or a second 10BASE-T or 100BASE-TX connection.

Ethernet Alliance

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.

IP camera

network cameracamerasIP cameras
This allows a single cable to provide both data connection and electric power to devices such as wireless access points, IP cameras, and VoIP phones.

Microsemi

Silicon GeneralacquiredPowerDsine Ltd.
PowerDsine, acquired by Microsemi in 2007, has been selling midspan power injectors since 1999 with its proprietary Power over LAN solution.

Phantom power

phantom powerphantom-poweredphantom powering
This is similar to the phantom power technique commonly used for powering condenser microphones.

PowerDsine

PowerDsine, acquired by Microsemi in 2007, has been selling midspan power injectors since 1999 with its proprietary Power over LAN solution.
Its initial products were Ringing (telephony) generators, and it also developed xDSL Remote Power Feeding Modules, before inventing Power over Ethernet's (PoE) precursor Power over LAN.

Category 3 cable

Cat 3category 3 cableCategory 3
The IEEE standards for PoE require category 5 cable or better for high power levels but allow using category 3 cable if less power is required.
The original Power over Ethernet 802.3af specification supports the use of cable, but the later 802.3at Type 2 high-power variation does not.

Cisco Discovery Protocol

CDP
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).
The information contained in CDP announcements varies by the type of device and the version of the operating system running on it. This information may include the operating system version, hostname, every address (i.e. IP address) from all protocol(s) configured on the port where CDP frame is sent, the port identifier from which the announcement was sent, device type and model, duplex setting, VTP domain, native VLAN, power draw (for Power over Ethernet devices), and other device specific information.

Ethernet

ethernetwirednetworking
Power is supplied in common mode 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.

Raspberry Pi

Raspberry PiRaspbianRaspberry Pi 2
On Pi Day 2018 model 3B+ appeared with a faster 1.4 GHz processor and a three times faster network based on gigabit Ethernet (300 Mbit / s) or 2.4 / 5 GHz dual-band Wi-Fi (100 Mbit / s). Other options are: Power over Ethernet (PoE), USB boot and network boot (an SD card is no longer required).

Building automation

building automationintelligent buildingsmart building
Recent IEEE standards (notably IEEE 802.15.4, IEEE 1901 and IEEE 1905.1, IEEE 802.21, IEEE 802.11ac, IEEE 802.3at) and consortia efforts like nVoy (which verifies IEEE 1905.1 compliance) or QIVICON have provided a standards-based foundation for heterogeneous networking of many devices on many physical networks for diverse purposes, and quality of service and failover guarantees appropriate to support human health and safety.

Emergency communication system

emergency communication systememergency communication systemscommunication systems
Some all-in-one devices, such as Advanced Network Devices' PoE (Power over Ethernet) devices, which save costs in combining multiple features in one device, installation, and operation.

Reolink

It produces indoor and outdoor IP surveillance cameras and systems, including PoE, wireless and battery powered cameras.

Home network

home networkhome networkingsmart appliance

Fibre to the office

fibre to the officeFTTO
Typically, the switch has up to five twisted pair ports supporting Power over Ethernet (IEEE 802.3af, 15.4W per Port) and Power over Ethernet Plus (IEEE 802.3at, 30W per Port).

Ethernet Powerlink

POWERLINK
This protocol has nothing to do with power distribution via Ethernet cabling or power over Ethernet (PoE), power line communication, or Bang & Olufsen's PowerLink cable.

ProCurve Products

Core
Powered by a combination of either 875W or 1500W PSUs, to provide a maximum of 3600W (5400W using additional power supplies) of power for PoE.

Perry Marshall

Though limited on the topic of mobile networking, its coverage of the basics, and in particular power over Ethernet, became widely accepted.