How does PoE lighting work?

How does PoE lighting work?
5 min read
14 October 2022

Networking "all over the world" or rather "all over the building" is the idea, which will also be of great importance in connection with the communication cabling of a building, especially a new building. The call to provide additional network connections - possibly in large numbers - in addition to the typical office rooms and areas is getting louder and louder.

Not each of these network connections has to be implemented with the help of a cable, on the contrary. It can be assumed that in order to save countless cables, the preferred medium will be wifi, regardless of the reliability and performance of this medium.

But let's not be fooled, access points also have to be connected with a cable and with a correspondingly high density of access points, a large number of cables are still required, which transport both data and power.

The IEEE 802.3af standard was the very first PoE standard to be introduced. The applications that were mostly suitable for PoE were ceiling-mounted access points, Voice-over-IP phones or  surveillance cameras.

PoE is a technology that can transmit both data and power over a single standard Ethernet cable. It enables the use of network cables such as Cat5/Cat5e/Cat6 cables to provide data connections and electrical power for wireless access points, IP cameras, VoIP phones and other power devices (PDs).

Using PoE technology, we can easily deliver power to remote indoor or outdoor PDs without having to install additional electrical infrastructure or provide power outlets at each endpoint.

Power over Ethernet

The main advantage of PoE is that you can save on a power supply cable and thus install Ethernet-connected devices in places that are difficult to access or in areas where many cables would interfere. The power supply to the device does not have to be supplied separately with a power cable and adapter or solved with a battery.

Instead, the energy the device needs is taken directly from the network. In addition to the data signals, current must also be fed into the data line – usually at a central point, in the network distributor.

This means that on the one hand installation costs can be saved, and on the other hand the use of a central uninterruptible power supply (UPS), which is easy to implement, can increase the reliability of the connected devices.

PoE is used by specific network devices that require only a small amount of power. It is typically used in IP phones, small hubs, cameras, small servers or in wireless transmission devices such as WLAN access points or Bluetooth devices.

Why should you use Power over Ethernet?

In addition to the advantages mentioned above, there are some other attractive reasons for using PoE.

Time and cost savings:

By using PoE in the network, no electrical cables and sockets need to be laid for PDs. This will help save many power wiring costs, especially when there are many PDs in the network. Additionally, there is no need to hire a qualified electrician for the PoE network, saving you time and money on electrical installations as well.


Since Ethernet network cables are easier to install than electrical ones, PoE allows us to install PDs almost anywhere, even beyond the reach of outlets. This offers the user great flexibility when setting up and repositioning end devices.


PoE power comes from a central and universally compatible source rather than a collection of distributed wall adapters. It can be backed up or controlled by an uninterruptible power supply (UPS) to easily disable or reset devices. In this way, the PDs run as usual even if the Power Sourcing Equipment (PSE) fails.

How does PoE work?

Devices that take their power from PoE request the required power level via an initialization sequence. This sequence starts when a low voltage is put on the cable by the according to power source. If a PoE device is attached to the other end of the cable, it will be detected during this initial sequence.

As soon as the current flow signals that a resistance of at least 25,000 ohms is run through the device, the sequence is automatically initiated by the power supplier and the powered device together.

There are basically two ways  how devices can signalize their requirements in terms of power: Either they exchange a series of electronic pulses with the used power source or they use Link Level Discovery Protocol (LLDP) or IEEE 802.1ab. This sets certain parameters that the devices exchange with each other to find out the type and level of performance that is necessary for proper functionality.


It becomes visible that PoE technology is increasingly being applied more and more worldwide. The technology provides an interesting perspective and shouldn't be overlooked.


People who are active in network architecture and development should by any means have PoE lighting on the map and understand its basic functionality to be able to determine when and where the implementation of PoE makes sense.



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jason rany 78
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