All About PoE. Commonly Asked Questions About PoE

by sogrow team

All About PoE. Commonly Asked Questions About PoE

What is Power Over Ethernet (PoE), and what is it used for? PoE is a function related to the Internet network. Allows Ethernet network cables, internet connection, and power supply to be transmitted over a single Cat5e / Cat6 Ethernet cable. PoE technology is based on the IEEE 802.3af and 802.3at standards. It is these standards that, in particular, allow compatibility between different peripheral devices.

Examples of PoE compliant devices are power supply devices (such as PoE injectors) and powered devices (IP phones, surveillance cameras, etc.). So this article will be about PoE technology, especially video surveillance.


General Information on PoE

Power over Ethernet (PoE) is a technology that was developed for private or commercial networks. This is based on the use of Ethernet cables. These are what allow the electrical current needed to power any device to flow through data cables instead of power cables.


Sources and general information about PoE

Thus, the Ethernet cable allows the transport of data from the Internet as well as the power supply. This minimizes the number of cables that must be connected to install a device on the network. PoE appeared in 2003 to support devices like IP phones. Later, PoE made device installation easier and more flexible, especially on ceilings.

For PoE to work, an electrical current must flow through the data cable. This separates the energy from the data transmission so that one does not interfere with the other. Electricity enters the wire through a component called an injector. If the device on the other end of the cable is PoE-enabled, it will function properly without modification. 4,444 devices built to the 2003 standard initially provided enough power for most devices in the early 2000s. But they couldn't provide enough power for other types of technology, such as security cameras. Over time, Category 5 (and better) Ethernet cables have overcome many limitations.


PoE Standards

The IEEE recently standardized the 802.3bt standard. 802.3bt PoE, also known as Next Generation PoE, can provide enough power to support LED lighting, CCTV systems, and other peripherals. It also defines a way to deliver two different power levels at the same time. Now that an industry-standard has finally been established, the use of PoE technology will continue to increase and play an important role in home automation.


What is the benefit of PoE?

Power over Ethernet (PoE) allows the installation of remote or external devices without being connected to the power supply. This means that more areas can be supplied without the need for additional electrical infrastructure or electrical outlets. The devices can be installed without hiring an electrician, and since Ethernet cables still cost less, PoE-based systems are much cheaper and more efficient.

PoE benefits both individuals and businesses for 5 main reasons: lower installation costs, secure installations, responsive deployments, data collection capabilities, and productivity improvements. The advantages of PoE mainly relate to the connection of products via a single cable.


How does PoE work?

The operation of PoE is not very complicated. It is also necessary for this to have the right devices. For that, we will discuss it a little below. In this section, we are going to talk about two main ways to power a connected device. Let's take the example of a PoE compliant surveillance camera.


An illustration without PoE: classic surveillance camera connection

Example no. 1 (yellow box) represents the simplest type of connection concerning the connection of a surveillance camera. On the one hand, there is the power supply (in black) and the connection to the internet network (green line). In itself, this type of installation is very good, but in particular, it requires an outlet near the camera. For connection to the Internet, it is possible via direct connection to the box or via a CPL socket.’

What changes with PoE: Connection through a PoE injector to a surveillance camera

The second example (in purple) is the perfect illustration of what people prefer (individuals, SMEs, companies, etc.). In this case, a PoE injector is usually used. The latter is powered through a socket and also connects to the internet box (or to a CPL socket). And only the Ethernet cables come out of the PoE injector and connect to the surveillance cameras. As explained in Example 1 (yellow square), a surveillance camera usually needs two connections when installed: one for the power supply and one for the connection to the Internet network. If the camera supports PoE, it is only necessary to establish the network connection, as it is also powered by this cable.

Some people who have a large network (or have many devices to connect to) choose option 3 (in blue). Here the connected devices depending on the PoE injectors, which in turn are subdivided by Ethernet ramps.


Commonly Asked Questions About PoE

PoE is very good, but there are many unanswered questions. This section is likely to provide answers to the various questions about PoE.


How do I connect a PoE injector?

To connect a PoE injector, nothing is easier. In this part, we take the Tenda TEF1105P. This PoE injector can supply power to up to 4 peripheral devices (63W max). The power supply is located at the rear of the injector. It has to be plugged in. This allows the PoE injector to be powered and then redistributed power.

Second, the injector must be connected to the network. So you need to connect an Ethernet cable to jack 5. Then there are the other four jacks. The latter allows the connection of up to 4 peripheral devices (63 W in total for the four). Voila, it's not that complicated!


Why does PoE save installation costs?

The installation costs of PoE are much lower than the installation cost of traditional cables. This is mainly because there is no need for an outlet near each device. Therefore, there is no need to cut the walls, drill outlets for the outlets, etc. With PoE, you put the injector in one place, and all you have to do is unroll the ethernet cable at the device location. It's over.


Why is the PoE implementation so responsive?

PoE devices adapt to changing environments. They can simply be moved and reconnected at the injector level and easily integrated into changing network configurations. PoE is "plug and play" (I-plugin, it works).


What if my PoE injector is too far from my internet box?

For various reasons, particularly architectural, PoE injectors are not easy to install. This type of difficulty occurs mainly in multi-story apartments (or professional offices). Some people want to install surveillance cameras, but it would end up requiring a lot of drilling, etc. So drop the idea. What a pity! In fact, with PLC technology, it is quite possible to connect a PoE injector to a PLC socket. In particular, this helps to distribute the number of places to install surveillance cameras.


What are the limits of PoE?

There are few limits for PoE. However, they must be taken into account when installing PoE injectors. First, simple PoE transmits data over a distance of 100 meters. The power supplied by the injector must be taken into account to ensure a correct supply of the different connected devices.

A PoE injector can transmit power as well as internet data up to 100 meters away, regardless of where the power is injected. The limitation is not due to the injector. These are the Ethernet cabling standards that limit to 100 meters. For basic use, whether for an individual or an SME, such a distance is largely sufficient to transmit data.


What maximum power can a PoE injector deliver per port?

When buying, it is normal to ensure that the maximum power of a PoE injector is sufficient for all devices. To do this, you need to identify the specifications of each product that will be connected to a port to see if you are getting the performance you need. Find these developed levels in the next section. PoE devices deliver power by IEEE 802.3 generation. Each generation is identified by the extension: "af", "at" or PoE + and "bt" or "UPoE". The following table compares the maximum power that each type of PoE can deliver at the port level.

Devices that use the PoE function to receive data and connect to the Internet are mostly communication products (IP phones, surveillance cameras, home automation products, etc.). Here is a list of examples. Remember, this list continues to grow as more people adopt PoE and manufacturers continue to prioritize the development of these products.


What is PoE +?

Power over Ethernet Plus (PoE +) is also known as PoE 802.3at. With PoE +, it doubles the power (30W) at the port over a twisted pair Ethernet cable. This is because the original IEEE 802.3af PoE offers 15.4 W. In summary, the big difference between PoE and PoE + is that the 802.3at standard provides more power per device.


The different types of power over Ethernet in PoE

A PoE injector can be useful in many cases. If you are an individual or an administrator of SMEs, buying and installing a PoE injector is easy. Generally, the purpose of such a product is to connect surveillance cameras or a video doorbell to it. For the most basic use, it is best to invest and install wired cameras. Also, PoE cameras are generally preferred for outdoor use.