What is PoE?

Power over Ethernet

Power over Ethernet (PoE) makes it possible to supply network-compatible devices such as cameras or access points with power directly via the network cable.

Supplying large networks with power or implementing new devices in them sometimes poses challenges in terms of the required power supply. Network-compatible devices sometimes only require a small amount of power, which is why a lot of reactive power is generated by the power supply units used, which cannot be utilised by them. Furthermore, existing server rooms often do not have additional sockets to expand a network in a meaningful way. The standardised Power over Ethernet (PoE) method provides a remedy for such problems.

How is the energy transmitted via the Ethernet cable?

Data and power for the energy supply are transmitted together via a cable to the end device (typically IP telephones, access points or IP cameras). Ethernet cables are eight-core. With older network standards, PoE uses two of the wire pairs not used for data transmission. With older PoE standards, two of the wire pairs not used for data transmission are used. With newer standards, which also provide more power, the power is fed in via four wire pairs.

PoE-capable distribution devices, known as power sourcing equipment (PSE), are required so that electricity can flow through the network at all. These can be divided into two categories: PoE switches and PoE injectors.

A PoE switch works like a normal network distributor, but with the difference that the ports also provide a power supply. Problems can sometimes occur if connected end devices are not PoE-compatible. Overvoltage and damage can then occur during operation. Injectors, on the other hand, can be used much more flexibly.

The PoE injector is connected between a conventional switch and the participants in the network. Data signals are therefore picked up by the distributor and only then fed in with additional power. This has the advantage that only those ports in the existing switch that really need the additional power supply need to be equipped with PoE.

Standards for Power-over-Ethernet (PoE)

As the functions of the end devices increase, so do their energy requirements, which is why there are several standards that provide different usable power. There are standardised power classes for this:

IEEE 802.3af (PoE) provides 15 W output power or up to 12.95 W at the end device.
IEEE 802.3at (PoE+) provides 30 W output power or up to 25.5 W at the end device.
IEEE 802.3bt (PoE++ or 4PPoE) delivers 90 W output power or up to 71.3 W at the end device.

Class	Standard	Output voltage	Max. Output voltage during operation	Max. Power supply (PSE)	Minimum power withdrawal (PD)
0	IEEE 802.3af	36 - 57 V	350 mA	15,4 W	0,44 - 12,96
1	IEEE 802.3af	37 - 57 V	351 mA	4,0 W	0,44 - 3,84 W
2	IEEE 802.3af	38 - 57 V	352 mA	7,0 W	3,84 - 6,49 W
3	IEEE 802.3af	39 - 57 V	353 mA	15,4 W	6,49 - 12,95
4	IEEE 802.3at	42,5 - 57 V	600 mA	25,5 W	12,95 - 25,50
5	IEEE 802.3bt	42,5 - 57 V	2× 960 mA	45 W	40 W
6	IEEE 802.3bt	42,5 - 57 V	2× 960 mA	60 W	51 W
7	IEEE 802.3bt	42,5 - 57 V	2× 960 mA	75 W	62 W
8	IEEE 802.3bt	42,5 - 57 V	2× 960 mA	90 W	71 W

Simple expansion of existing networks

Probably the easiest way to retrofit your existing network with PoE is by integrating POE injectors or injector hubs. Thanks to PoE injectors, retrofitting is particularly easy and requires no changes to your existing network. This saves you time, money and effort.

Simple retrofitting: PoE injectors make it possible to integrate PoE-capable devices into an existing network without having to replace the switch.
Cost-efficient: You save the cost of installing separate power lines, as power and data are transmitted via the same cable.
Flexibility in placement: PoE injectors allow devices to be used in locations without nearby sockets, such as on ceilings or outdoors.
Plug-and-play: They are easy to install and require no special configuration - ideal for quick and uncomplicated implementations.
Stability and safety: PoE injectors provide a reliable power supply with integrated protection mechanisms against overload, overvoltage and short circuit.
Compatibility: They work easily with standard Ethernet cables and PoE-capable devices, regardless of brand or model.

InLine® PoE+ Gigabit network injector hub 8 port (8x PoE+), 1Gb/s, 19" 1U

8-port PoE+ injector hub with up to 30 W power per port (total up to 240 W) Supports IEEE 802.3af/at for PoE and PoE+ devices such as IP cameras & access points Wireless design for noiseless operation in a 19" rack (1U) Triple protection: overcur...

Item no.: 32308H

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Item no.: 32305R

InLine® PoE+ Gigabit Network Switch 24 port, 1 Gb/s, 2xSFP,19"1U(incl. brackets)

PoE++ switch with 16 ports and SFP uplink for flexible power and data supply Supply high-power devices: PoE++ up to 60 W (ports 1-4), PoE+ up to 32 W (ports 5-16), 300 W budget. Safely bridge long distances: 2x SFP for fiber uplinks at 1000 Mb/s. Sim...

Item no.: 32316P

InLine® PoE+ Gigabit Injector Hub 16 Port PoE+, 19"1U, brackets included, 2 fans

PoE+ retrofit for 16 ports without replacing the switch Fast upgrade without replacing the infrastructure: You continue to use existing switches and provide PoE centrally. Powerful for cameras and Wi-Fi: You power 16 devices via PoE+ with up to 30 W ...

Item no.: 32316H

The right cable

Another very important aspect for an error-free and resilient PoE network is the selection of the correct cable; before installation, you should consider the cable length, the wire cross-section and the possible heating of the network cable. The higher the current flow, the more heat is generated by the resistance in the cable. This can impair data transmission. It is therefore important to check in advance what load the cable can withstand and how the heat generated can be safely dissipated. The higher the wire cross-section (AWG number), the more resilient the cable.

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