Allied Telesis AT-S112, AT-GS950/16PS manual 284

Chapter 22: Power Over Ethernet (PoE)

Overview

Power Sourcing Equipment (PSE)

Powered Device (PD)

PD Classes

Power Budget

The AT-GS950/16PS switch features Power over Ethernet (PoE) on the 10/100Base-Tx ports on ports 1 - 16. PoE is used to supply power to network devices over the same twisted pair cables that carry the network traffic.

The main advantage of PoE is that it can make installing a network easier. The selection of a location for a network device is often limited by whether there is a power source nearby. This constraint limits equipment placement or requires the added time and cost of having additional electrical sources installed. However, with PoE, you can install PoE- compatible devices wherever they are needed without having to worry about whether there is power source nearby.

A device that provides PoE to other network devices is referred to as power sourcing equipment (PSE). The AT-GS950/16PS switch is a PSE device which provides DC power to the network cable and functions as a central power source for other network devices.

A device that receives power from a PSE device is called a powered device (PD). Examples include wireless access points, IP phones, webcams, and even other Ethernet switches.

PDs are grouped into five classes. The classes are based on the amount of power that PDs require. The AT-GS950/16PS PoE switch supports all five classes listed in Table 6.

Table 6. IEEE Powered Device Classes

	Class	Maximum Power Output	Power Ranges of the PDs
		from a Switch Port
0		15.4W	0.44W to 12.95W
1		4.0W	0.44W to 3.84W
2		7.0W	3.84W to 6.49W
3		15.4W	6.49W to 12.95W
4		34.2W	25.5W to 38.9W

Power budget is the maximum amount of power that the PoE switch can provide at one time to the connected PDs. The AT-GS950/16PS can supply up to 855 Watts maximum.

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