Power over Ethernet, or PoE for short, is the name of the technology with which devices can be supplied with power as well as data via the network cable. This saves separate cabling for the power supply. There are various PoE standards that categorize the different maximum power that is transmitted via the network cable.

The individual PoE standards have been certified by the Institute of Electrical and Electronics Engineers and therefore also begin with the abbreviation IEEE.

The first PoE standard IEEE802.3af was certified in 2003 and is designed for a current of 12.9 watts at a voltage of 44-57 volts.

The second PoE standard was certified in 2009 with the designation IEEE802.3at and is also called PoE+. It is designed for a current of 30 watts at the same voltage, 44-57 volts.

The latest PoE standard was certified in 2018 and is called IEEE802.3bt. This standard is also called 4PPoE or PoE++. 4PPoE, written out as 4 Pair Power over Ethernet, refers to the use of the network cable. This consists of 4 pairs of wires and IEEE802.3bt uses all 4 pairs to transmit the power of up to 100 watts at a voltage of 50-57 volts.

Here again a small overview with extra information to better distinguish everything

PoE+ is the second certified PoE standard after PoE. The official name for the PoE+ standard is IEEE802.3at. With PoE+ it is possible to supply end devices with a power of approx. 25 watts. As with the first standard IEEE802.3af a voltage of 44 – 57 volts is also used.

PoE++ or 4PPoE is the latest PoE standard, which was certified with the designation IEEE802.3bt in 2018. IEEE802.3bt or PoE++ is designed for an output of up to 100 watts and transmits this with a voltage of 50 – 57 volts.

Passive PoE is a PoE standard that is not certified by the IEEE. Here, a voltage of 24 volts and exclusively pinout mode B (wire pair 4/5 positive voltage, 7/8 negative voltage) is used.

In addition to the data supply, you need a device that supplies your network cable with power. These devices are called Power Sourcing Equipment (PSE for short). and can be divided into PoE Switches and PoE Injectors. If you would like more information about the different PSEs, then take a look at our PoE Wiki.

In contrast to sockets, only a low voltage is used for the power supply via the network cable. Just 44 to 57 volts and with passive PoE even only 24 volts. Since this is a comparatively very low voltage, no electrician is required for the installation of PoE. Electrical installations, such as power cables, have a voltage of 240 volts and these may only be carried out by certified electricians.

Cables with an RJ45 connection are suitable for Power over Ethernet, i.e. any common Network, Ethernet or LAN cable, from category 5 / Cat5 cables. So you can use any commercially available Cat5, Cat5e, Cat6 or Cat7 cable for your PoE network.

Depending on the pinout mode used, the 4 wire pairs in a network cable are used differently. In the pinout mode A, the positive voltage is transmitted over the wires 1/2 and the negative voltage over the wire pair 3/6. In pinout mode B, the positive voltage is transmitted over the wire pair 4/5 and the negative voltage over the wire pair 7/8. Since wire pairs remain unused in these two modes, they are also called spare pair modes. It is different with the latest PoE standard IEEE802.3bt, also called 4 Pair Power over Ethernet or 4PPoE for short. As the name suggests, all wire pairs are used simultaneously to transmit the increased amount of electricity of up to 100 watts.

Depending on the standard, either 2 or all 4 wire pairs of a network cable are used. You can find a more detailed description under the question “Which cores of a network cable are used for PoE?”

PoE capable means that your device can receive power as well as data via its network connection or port. If your end device is not PoE capable, you should not connect it to a PoE network device, as you risk a short circuit. If you want to be on the safe side, you should use an active switch or injector, as this checks with a short signal whether your device (PD) is PoE capable.

With a PoE adapter, devices without an RJ45 or network connection, such as tablets, can be supplied with data and power using PoE. A PoE Adapter usually has an RJ45 connection or network connection as an input and an output suitable for the end device, such as USB-C or Apple Lightning.

A PoE Splitter works similarly to a PoE Adapter. The difference to the Adapter is that the PoE Splitter has two outputs. One output is the typical RJ45 or network connection for data supply and the second output is for the power supply of the end device, which can be, for example, a USB-C or a 2.1mm jack connection. So does your end device have two inputs, RJ45 and e.g. 2.1mm, a PoE splitter is the right choice for data and power supply via PoE.

IEEE802.3af is the official name for the first PoE standard, which was certified by the Institute of Electrical and Electronics Engineers (IEEE) in 2003. If a device is IEEE802.3af certified, this means that this device can receive data and power via the network cable or, in the case of Switches and Injectors, transmit them. The power is around 15 watts at a voltage of 44-57 volts, because the IEEE802.3af standard is designed for this.

Like IEEE802.3af, IEEE802.3at is also an official name for a PoE standard. This standard was certified by the IEEE in 2009 and is also called PoE+. As you can imagine, IEEE802.3at (PoE+) is designed for a slightly higher output, namely for up to 30 watts at the output port. IEEE802.3at is also backwards compatible with IEEE802.3af. This means that you can use IEEE802.3af end devices with an IEEE802.3at certified PoE Switch or Injector.

The latest PoE standard IEEE802.3bt was certified by the IEEE in 2018 and is also called PoE++ or 4PPoE. 4PPoE, written out as 4 Pair Power over Ethernet, refers to the use of the network cable. This consists of 4 pairs of wires and IEEE802.3bt uses all 4 pairs of wires to transmit the power of up to 100 watts at a voltage of 50-57 volts.

RJ45 is the name for the plug connection of a common network, LAN or Ethernet cable, over which most devices receive data nowadays.

Like every common Network Switch, a PoE Switch is used for data distribution and management in an Ethernet Network. The only difference to a normal Ethernet Switch is that the PoE Switch also transmits power via the Network cable in addition to the data.