Allied Telesis AT-S62 - Manual (Page 320)

Chapter 20: Power Over Ethernet
Section II: Advanced Operations 320
PoE
Implementation
on the
AT-8524POE
Switch
A standard Ethernet twisted pair cable contains four pairs of strands for a
total of eight strands. 10/100 Mbps network traffic requires only four
strands, leaving four strands in the cable unused. The strands that carry
the network traffic are 1, 2, 3, and 6, and the spare strands are 4, 5, 7, and
8.
The IEEE 802.3af standard, which is the IEEE standard for PoE, describes
two methods for implementing PoE over twisted pair cabling. One
method uses the same strands that carry the network traffic and the
other the spare strands.
The PoE implementation on the AT-8524POE switch transmits power
over the same strands that carry the network traffic. The power transfer
does not interfere with the network traffic. The power and the network
traffic can coexist on the same strands simultaneously.
Powered devices that comply with the IEEE 802.3af standard typically
support both methods of power delivery methods. So you should not
need to be concerned about whether a powered device is compatible
with the switch’s power delivery method. So long as a powered device is
compliant with the standard, it should be able to receive its power from
the switch.
The PoE feature on the switch should also work with most legacy
powered devices as well. A legacy device is a node that was
manufactured before the IEEE 802.3af standard was completed and,
consequently, may not adhere to the standard.
Power Budgeting
The power supply in the AT-8524POE switch can provide up to a total of
400 watts (W) of PoE to Ports 1 to 24 on the switch. (PoE is not supported
on expansion modules.) In a maximum load configuration, where all
ports are connected to a powered device and all of the devices require
the maximum of 15.4 W, the total power requirement would be
approximately 370 W. This is below the maximum power available.
The fact that the maximum possible power requirement falls below the
maximum amount of power available means that you can connect
powered devices to all the ports on the switch (excluding optional
expansion ports) without exceeding the available power, even when all
the powered devices require the maximum of 15.4 W.
You can, using the AT-S62 management software, disable PoE on a per-
port basis. You can also reduce the maximum amount of power a port
can receive, from the maximum of 15.4 W. However, configuring PoE on
an AT-8524POE switch will probably not be necessary. As already
mentioned, the power supply in the switch can provide enough power
to meet the needs of all 24 base ports, even when all are all connected to
power devices requiring the maximum of 15.4 W. Additionally, a switch
port can automatically determine for itself whether the device