3.3 Concepts of PoE
Power over Ethernet (PoE) is the ability to deliver up to 48 VDC of power over the same copper cable as Ethernet. Two primary elements are required in order to implement PoE. They are:
1. Power sourcing equipment (PSE) - the LAN switch or source power delivered over Ethernet
2. The powered device (PD) - the end device that accepts and uses power from the Ethernet cable for its operation
Power over Ethernet or PoE technology describes a system to safely transfer electrical power, along with data, to remote devices over standard data cables in an Ethernet network (Cat3/Cat5/Cat5e/Cat6 ).
Power is remotely supplied from a central location (e.g. wiring closet) for distances under 100 meters without the Ethernet devices having to be individually powered by an AC outlet.
PDs include IP Phones, Wireless LAN Access Points, IP Security Cameras and various other network devices
The IEEE has created a standard for PoE called 802.3af, for PoE+ it's referred to as 802.3at. These standards describe precisely how a powered device is detected and also defines two methods of delivering Power over Ethernet to a given powered device.
Nowadays, PoE is used for many devices. For example:
1. VoIP phones
2. IP cameras
3. Wireless access points
4. IoT devices
5. PoS devices
6. Raspberry Pi
7. Arduino devices
8. Small routers and switches
A device that is powered by PoE is called a powered device (PD).