Power Over Ethernet; Poe Standards - Allied Telesis AT-GS924MX Installation Manual

Chapter 1: Overview

Power over Ethernet

PoE Standards

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The AT-GS924MPX and AT-GS948MPX Switches feature Power over
Ethernet (PoE) on the 10/100/1000Base-T ports. PoE is used to supply
power to network devices over the same twisted pair cables that carry the
network traffic.
The main advantage of PoE is that it can make it easier to install a
network. The selection of a location for a network device is often limited by
whether there is a power source nearby. This often limits equipment
placement or requires the added time and cost of having additional
electrical sources installed. But with PoE, you can install PoE-compatible
devices wherever they are needed without having to worry about whether
there are power sources nearby.
A device that provides PoE to other network devices is referred to as
power sourcing equipment (PSE). The AT-GS924MPX and
AT-GS948MPX Switches act as PSE units by adding DC power to the
network cable, thus functioning as a central power source for other
network devices.
Devices that receive their power from a PSE are called powered devices
(PD). Examples include wireless access points, IP telephones, webcams,
and even other Ethernet switches.
The switch automatically determines whether or not a device connected to
a port is a powered device. Ports that are connected to network nodes that
are not powered devices (that is, devices that receive their power from
another power source) function as regular Ethernet ports, without PoE.
The PoE feature remains activated on the ports, but no power is delivered
to the devices.
The AT-GS924MPX and AT-GS948MPX Switches support these PoE
standards:
PoE (IEEE 802.3af): This standard provides up to 15.4 watts at the

switch port to support powered devices that require up to 12.95
watts.
PoE+ (IEEE 802.3at): This standard provides up to 30.0 watts at

the switch port to support powered devices that require up to 25.5
watts.