Allied Telesis AT-SBx81CFC960 - Manual (Page 58)

Chapter 2: Ethernet Line Cards
58 Section I: Hardware Overview
support PDs that receive power using Alternative A.
PDs that comply with the IEEE 802.3af and 802.3at standards are
required to support both power delivery methods. However, non-standard
PDs and PDs that were manufactured before the completion of the IEEE
802.3af and 802.3at standards and that support only Alternative B will not
work with the AT-SBx81GP24 PoE Line Card.