Power over Ethernet - IEEE 802.3af

The networking of industrial installations is an important and steadily expanding topic in the field of automation. Just as office networking once did, Ethernet networking is now advancing into industry and making strides to replace existing standards such as Profibus. A number of companies now offer networking solutions under the name Industrial Ethernet. Their offers range from small entry level switches through modular Gigabit switches right up to wireless LAN (WLAN) access points. The IEEE 802.3af standard, which supports the simultaneous network transfer of data and power, was introduced to reduce installation costs and provide more flexible networking facilities. It means that, instead of separate network cables for data, power and telephones (VoIP), everything can now be conveyed via a single LAN cable. Many offices are already successfully using equipment such as IP telephones and access points with PoE functionality. Unlike office networks with their star-shaped network structures, industrial applications generally use a linear arrangement. The industrial use of Power over Ethernet (PoE) is somewhat restricted by the fact that the PoE standard describes only point-to-point connections.

Basic principles of PoE

The Power over Ethernet (PoE) facility, which is standardized under IEEE 802.3af, was developed to reduce the cost of network planning, cabling and installation. The equipment is powered directly over the data line (e.g. for distances up to 100m via a CAT 5/5e cable). PoE makes network planning flexible and independent of switch cabinets and power sources, and also saves additional outlay for power and telephone networks (VoIP). The principal advantage of Power over Ethernet is that it renders power cables unnecessary, so that equipment with Ethernet interfaces can be installed even in inaccessible locations or where extra cables would be in the way. This not only makes it possible to make massive savings on installation costs, it also facilitates the operation of uninterruptible power supply systems (UPS) to improve the reliability of the attached equipment. PoE is primarily used for low-powered terminal devices, typically IP telephones, cameras and wireless transmission equipment such as WLAN or Bluetooth access points, but it can also provide a redundant power supply for switches to increase the network’s reliability. For example, if the power supply to a switch should fail, it can continue to operate under PoE power, which markedly increases the availability of the network. PoE can be used in four-wire or eightwire networks. In four-wire networks can only be used phantom power, but eight-wire networks can use both phantom and spare-pair power. Power over Ethernet is specified and standardized by IEEE 802.3af standard, which subdivides devices into two groups

1. Power over Ethernet PSE (power sourcing equipment): this type of device functions as a power source and supplies PoE PD devices with power via the data line.

2. Power over Ethernet PD (powered device): this type of device consumes power that it receives via the data line from a PoE PSE device.


Compact Industrial Switches (managed) - PoE

Configurable managed switches - the OpenRail System with PoE Technology.

MSP30-24040 with modules

Modular Industrial Switches - PoE

Configurable mangaged industrial switches with up to 24 PoE ports - the MICE modular system.


IP 67 Industrial Switches - PoE

OCTOPUS IP67 - the world’s first IP 67 PoE connectivity solution.


Ruggedized Switches - PoE

The MACH1000 substation switches offer high data rates and PoE power distribution in your industrial backbone.


Industrial Wireless LAN - PoE

The BAT Family with Wireless LAN Powered Devices.


PoE Power supplies

48 V PoE Power supplies for the Modular Industrial Switches (MICE).


Workgroup Switches - PoE/PoE plus

MACH100 series: MACH104 Gigabit/10 Gigabit Ethernet PoE Workgroup Switches with 22-24 Ports


Backbone Switches - PoE

The MACH 4000 Gigabit Switches as Power Sourcing Equipment (PSE) with up to 100 W.


Entry Level Industrial Ethernert Rail Switches

Flexible extension of networks with electrical and optical Fast Ethernet ports powered via PoE.


The new PRP (Parallel Redundancy Protocol) and HSR (High-availability Seamless Redundancy) protocols are two newly developed redundancy methods that significantly increase the availability and reliability of network connections.

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