Allied Telesis AT-GS950/8POE manual Minimum Power Maximum Power Class

AT-GS950/8POE Gigabit Ethernet WebSmart Switch Installation Guide

Power Budgeting The AT-GS950/8POE switch provides a maximum of 15.4 W of power per port on four of the eight ports for a total power consumption of 62 W, while at the same time furnishing standard 10/100 Mbps Ethernet functionality.

The AT-GS950/8POE switch power management functionality supports any combination of Ethernet ports (1-4) that supply power for IEEE 802.3af Class 0, 1, 2, or 3 powered devices up to a maximum of 62 watts, as described in Table 2.

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 62 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 4 in ascending order.

Table 2. 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

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-GS950/8POE switch is Alternative B, where power is transmitted over strands 4, 5, 7, and 8.

PDs that comply with the IEEE 802.3af standard typically support both power delivery methods. When a PD is compliant with the standard, it receives its power from the switch using either a straight or cross-over cable. The PoE feature on the AT-GS950/8POE switch works with most legacy PD’s as long as the device can be powered on pins 4, 5, 7, and 8.

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