Allied Telesis AT-S88 - Manual (Page 43)

AT-S88 Management Software User’s Guide
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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 standard for PoE, describes two
modes for delivering power to the powered device over twisted pair
cabling. Mode A uses the same strands that carry the network traffic.
Mode B uses the spare strands. The PoE implementation on the
AT-FS750/24POE Fast Ethernet Smart switch is Mode B, where power is
transmitted over strands 4, 5, 7, and 8.
Powered devices that comply with the IEEE 802.3af standard typically
support both power delivery methods. 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 long as the device can be powered by pins 4, 5, 7, and 8. 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.
PoE Operation
Modes
You can configure the ports to operate in either an automation-based or
allocation-based mode.
When you select automation-based power operation, the power
management function automatically determines the amount of power to
allow for the device. The switch does this by detecting the device and
determining its PoE class, from 0 through 4. The PoE class specifies the
maximum input power level for the device.
If you select allocation-based power operation, you must configure the
power allocation for each PoE port, up to 20,000 mW.
You can also prioritize the ports in the event there is not be enough PoE
power for all the powered devices. This feature helps ensure that the most
important powered devices connected to the switch will be guaranteed
power.