Allied Telesis 8000/8POE manual Minimum Power, Maximum Power, Class, Usage, the PSE, the PD

Chapter 1: Overview

Power Budgeting The AT-8000/8POE Fast Ethernet Switch provides a maximum of 15.4 W of power per port on six of the eight ports for a total power consumption of 95 W, while at the same time furnishing standard 10/100 Mbps Ethernet functionality.

The AT-8000/8POE smart power management functionality supports any combination of Ethernet ports (1-8) that supply power for IEEE 802.3af Class 0, 1, 2, or 3 powered devices up to a maximum of 95 watts, as described in Table 5.

Note

Power is supplied to the powered devices in the order that the ports are connected or on a first-come-first-served basis until the 95 watt limit is reached. If the switch is power cycled after the PoE devices are connected to the switch ports, the power is supplied to ports 1 through 8 in that order.

Table 5. IEEE 802.3af Class vs. Power Levels

		Minimum Power	Maximum Power
Class	Usage	Levels Output at	Levels Output at
		the PSE	the PD
0	Default	15.4W	0.44W to 12.95W
1	Optional	4.0W	0.44W to 3.84W
2	Optional	7.0W	3.84W to 6.49W
3	Optional	15.4W	6.49W to 12.95W

A port connected to a network node that is not a powered device (that is, a device that receives its power from another power source) functions as a regular Ethernet port, without PoE. The PoE feature remains enabled on the port but no power is delivered to the device.

Implementation 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 (1, 2, 3, and 6), leaving four strands in the cable unused (4, 5, 7, and 8).

The PoE standard, IEEE 802.3af, describes two alternative ways for delivering power to a powered device (PD) over twisted pair cabling. Alternative A uses the same strands that carry the network traffic.

Alternative B uses the spare strands. The PoE implementation on the AT-8000/8POE Fast Ethernet Switch is Alternative B, where power is transmitted over strands 4, 5, 7, and 8.

PD’s that comply with the IEEE 802.3af standard typically support both power delivery methods. So long as a PD is compliant with the standard, it

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