Allied Telesis AT-SBx31CFC960 - Manual (Page 61)

SwitchBlade x3106 Chassis Switch and AT-SBx31CFC960 Card Installation Guide
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The PoE implementation on the AT-SBx31GP24 Line Card is Alternative
A, in which power is transmitted over strands 1, 2, 3, and 6.
PDs that comply with the IEEE 802.3af and 802.3at standards typically
support both power delivery methods. However, some legacy PDs support
only one power delivery method. Legacy devices that only support
Alternative B will not work with the AT-SBx31GP24 PoE Line Card. Legacy
devices are nodes manufactured before the IEEE 802.3af and 802.3at
standards were completed and, consequently, may not adhere to the
standards.