Allied Telesis AT-9448Ts/XP (Basic Layer 3) - Manual (Page 39)

AT-9400 Series Gigabit Ethernet Switches Installation Guide
39
Power Over Ethernet
The following discussion applies only to the AT-9424T/POE Gigabit
Ethernet Switch.
The twisted pair ports on the AT-9424T/POE Switch feature Power over
Ethernet (PoE). PoE is a mechanism for supplying power to network
devices over the same twisted pair cables that are used to carry the
network traffic. This feature can simplify network installation and
maintenance because it allows you to use the switch as a central power
source for other network devices.
A device that receives its power over an Ethernet cable is called a
powered device. Examples of such devices can be wireless access points,
IP telephones, web cams, and even other Ethernet switches. A powered
device that is connected to a port on the switch receives both network
traffic and power over the same twisted pair cable.
There are several advantages that the PoE feature of the AT-9424T/POE
switch adds to the installation and maintenance of your network. First,
because the switch acts as the central power source for your powered
devices, adding an uninterruptible power source (UPS) to the switch
increases the protection not just to the switch itself from possible power
source problems but also to all of the powered devices connected to it.
This can increase the reliability of your network by minimizing the impact
to network operations from a power failure.
PoE can also simplify the installation of your network. A frequent issue in
selecting a location for a network device is whether there is a power
source nearby. This often limits equipment placement or requires the
added cost and time of having additional electrical sources installed. With
PoE, you can install PoE-compatible network equipment wherever they
are needed without having to worry about whether they are near a power
source.
The switch automatically determines whether or not a device connected to
a port is a powered device. A powered device has a signature resistor or
signature capacitor that the switch can detect over the Ethernet cabling. If
the resistor or capacitor is present, the switch assumes that the device is a
powered device.
Power Budgeting
The AT-9424T/POE Gigabit Ethernet Switch has a power budget of
approximately 370 W. It can provide a maximum of 15.4 W of power per
port on all of the 24 base ports.
The AT-9424T/POE Switch supports IEEE 802.3af Class 0, 1, 2, and 3
powered devices, listed in Table 8. The devices can be connected to the