Elimination of power cables
Since the end device is supplied with power by the LAN cable, you no longer need a power cable and thus reduce the tangled cables.
What is Power over Ethernet?PoE standardsThe advantages of PoEPoE methodsWhat do you have to consider?The technical terms
A brief introduction to Power over Ethernet
Power over Ethernet or PoE for short refers to the technology with which end devices such as cameras, tablets or IP telephones are not only supplied with data but also with power through the network cable. This eliminates the need for a power cable, you are free to choose the location of your devices and have a secure and stable LAN connection.
This technology is defined and standardized in the standards of the Institute of Electrical and Electronics Engineers, in short the IEEE standards.
These standards can be divided into three classes, which essentially differ in how much power is transmitted through the network cable. You can find more information here on our PoE standards page.
Find the right PoE standard for your project
The Institute of Electrical and Electronics Engineers, IEEE for short, is a global organization that organizes specialist conferences, publishes specialist journals and deals with the standardization of hardware, software and general technologies.
These standards include, for example, the IEEE 802.11 standard for wireless LAN, the IEEE 1284 standard for parallel interfaces and finally also the IEEE 802.3 standard for Ethernet technologies.
In the three standards IEEE 802.3af, IEEE 802.3at and IEEE 802.3bt, in addition to the three previous Power over Ethernet variants, the energy sources and end devices are also defined.
| IEEE standard | description | Output power | Useful power | Voltage | Pinout mode |
|---|---|---|---|---|---|
| IEEE802.3af | PoE | 15,4 watt | ~12,95 watt | 44-57 volt | A or B |
| IEEE802.3at | PoE+ | 30 watt | ~25,5 watt | 44-57 volt | A or B |
| IEEE802.3bt | PoE++ / 4PPoE | 100 watt | ~85 watt | 50-57 volt | A and B |
IEEE 802.3af
The IEEE 802.3af standard is the first Power over Ethernet standard and dates back to 2003. Devices with this PoE standard deliver an output power of 15.4 watts per port, with an output of approx. 12.95 watts arriving at the end device. The electricity is transmitted via the network cable from the energy source to the end device with a voltage of 44-57 volts. A standard network cable of the type Cat5, Cat5e, Cat6, … etc. with an RJ45 connector can be used. Please note the so-called pinout mode. The pinout mode determines from which cable pairs, within the network cable, power and data are transmitted. A device with the IEEE 802.3af standard can use mode A, mode B or mode A / B.
In addition to the technical specifications, the IEEE 802.3af standard also defines terms for the PoE devices used. Devices for power supply are Power Sourcing Equipment (PSE)and devices that receive power via PoE are Powered Devices (PDs).
IEEE 802.3at
After the IEEE 802.3af standard, the IEEE 802.3at standard followed in 2009. With this, the output power of the energy sources (PSE) increased from 15.5 watts to 30 watts per port. This standard also relies on an output voltage of 44-57 volts, also works with Cat5 or higher-quality network cables and uses one of the three pinout modes. Good to know: Devices that are IEEE 802.3at certified are downward compatible and also support the IEEE 802.3af standard.
IEEE 802.3bt
The IEEE 802.3bt standard is the newest of the three standards and was defined in 2018. This standard is often also called “PoE ++” or “4PPoE”. “4PPoE” is the abbreviation for “Four Pair Power over Ethernet” and thus describes the pinout mode or the transmission of power and data via the network cable. All four wire pairs of the cable are used at the same time to achieve the power of up to 100 watts that is transmitted via the network cable. This usage corresponds to the pinout mode A / B. In contrast to the IEEE 802.3af and IEEE 802.3at standards, the PSE assumes a voltage of 50-57 volts if the maximum output is to assume 100 watts. This standard is also backwards compatible with IEEE 802.3af and IEEE 802.3at.
Passive PoE
In addition to the standards defined by the IEEE, there is a fourth Power over Ethernet variant. Passive PoE uses an even lower voltage than the other variants, namely only 24 volts. In addition, exclusively pinout mode B is used to transport data and power to the end device (PD).
What advantages does Power over Ethernet offer you?
Which PoE method is the right one for your end devices?
In addition to the PoE standards, there are two basic methods of how PoE devices interact with one another. A distinction is made between passive PoE and active PoE devices.
Active PoE
With the active PoE method, the energy supplier (Power Sourcing Equipment / PSE) carries out a brief check as to whether the end device (Powered Device / PD) is PoE capable or not. If it can be charged via PoE, then data and power will be available via the network cable. If the end device is not PoE capable, only data is sent to the device.
A short example: You connect a non-PoE capable laptop to a network cable. The PSE, which uses the Active PoE method, sends a short signal to check whether the laptop is PoE capable. This signal, a short “handshake”, will tell the PSE that the laptop does not support PoE and only data will be transferred.
Passive PoE
With the term Passive PoE we do not mean the passive PoE standard in this case. This refers to the method of communication between PSE and PD. With the passive PoE method, the data and power are continuously transmitted from the PSE to the PD. No check is carried out to determine whether the PD is PoE capable.
Again to our example: The laptop that you connected to the network cable is still not PoE capable. You now connect your network cable that comes from your passive PSE. That means, data and electricity are transferred to the laptop. But your laptop doesn’t know how to handle the electricity. You run the risk of a short circuit in the laptop.
What to look out for …
PoE capability
There are now many end devices (PDs) that can receive power and data via the network cable. These devices are PoE capable, so there is no need for a further element, apart from a PoE Switch or PoE Injector, to supply your device with power via PoE.
Non-PoE capable devices are not able to use the power that comes over the network cable. So if power is to be transmitted over the network cable and the end device (PD) is not PoE capable, you run the risk of a short circuit.
It may still be possible to supply a non-PoE capable device with power via PoE. Depending on the PD, a PoE Adapter or a PoE Splitter is required for this.
PoE Adapter
A PoE Adapter is used with end devices such as a tablet.
The adapter has a PoE LAN connection and an output suitable for the end device, such as a USB-C or Lightning output. The incoming power and the data from the network cable are converted to a different output type.
PoE Splitter
A PoE Splitter takes the power and the data from the network cable and divides them between a suitable power and data output. The output then consists, for example, of a LAN connection and a 2.1 x 5.5mm connector. This means that end devices that are not PoE capable can be used without a socket nearby.
Brief explanations of terms that are often used in connection with Power over Ethernet.
4PPOE
Another name for the IEEE 802.3bt standard
802.3af
First PoE standard defined by the IEEE in 2003. Allows a power output of 15.4 watts at 44-57 volts.
802.3at
Second PoE standard defined by the IEEE in 2009. Power output has been increased from 15.4 watts to 30 watts.
802.3bt
Third PoE standard defined by the IEEE in 2018.
CAT5 cable
Network cable that is most commonly used today. CAT5 means Category 5 and is designed for an operating frequency of up to 100 Mhz.
Fast Ethernet
Ethernet with a data transfer rate of 1/10/100 Mbit/s
Gigabit Ethernet
Ethernet with a data transfer rate of up to 1000 Mbit/s
IEEE
The Institute of Electrical and Electronics Engineers
Pinout mode A
If a device uses pinout mode A, power and data are transmitted via wire pairs 1/2 and 3/6 of a LAN cable. The negative voltage runs through pins 1/2 and the positive through pins 3/6. The data are transmitted over the same wire pairs as the electricity, but do not stand in the way.
Pinout mode B
If a device uses pinout mode B, power and data are transmitted via the wire pairs 4/5 and 7/8 of a LAN cable. The negative voltage runs through pins 7/8 and the positive through pins 4/5. Data is transmitted over the remaining wire pairs 1/2 and 3/6. This pinout mode is mainly used for passive PoE devices.
Pinout mode A/B
If a device uses pinout mode A / B, power and data are transmitted over all four wire pairs of a LAN cable. This makes the pinout mode A / B compatible with devices that use mode A or mode B, but not all functions are supported. The IEEE 803.3bt / PoE ++ standard always uses this pinout mode to deliver and receive the requested power to the end device.
Patch cord
A patch cable is another term for a network cable with RJ45 plugs.
Passive PoE
Passive PoE is not a defined standard of the IEEE. This technique uses a voltage of 24 volts.
PD
PD = Powered Device is the term for end devices such as cameras, IP telephones, routers, etc. that are supplied with power by PoE.
Pinout Mode
Determines which pins of a network cable are used to transmit power and data.
PoE
Term for the technology with which powered devices (PDs) are supplied with data and power through the network cable. Complies with the IEEE 802.3af standard.
PoE+
Name for the second PoE standard that was defined by the IEEE in 2009.
POE++
Name for the third PoE standard that was defined by the IEEE in 2018.
PSE
PSE = Power Sourcing Equipment = devices for power supply such as PoE capable Ethernet Switches and PoE Injectors.
RJ45
Connection type / plug connection of network cables.
Twisted pair cable
Cables with twisted wire pairs like network cables.