Allied Telesis AT GS900/8POE, Руководство по установке

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Chapter 1: Overview
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Power over Ethernet
The twisted pair ports on the AT-GS900/8POE Gigabit Ethernet switch
feature Power over Ethernet (PoE). PoE is a mechanism for supplying
power to network devices over the same twisted pair cables used to carry
network traffic. This feature can simplify network installation and
maintenance by allowing 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. An example
of the latter is the unmanaged AT-FS705PD Ethernet switch from Allied
Telesis. A powered device connected to a port on the switch will receive
both network traffic and power over the same twisted pair cable.
There are several advantages that the PoE feature of the AT-GS900/
8POE Gigabit Ethernet 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-GS900/8POE Gigabit Ethernet switch provides a maximum of
15.4 W of power per port on four of the eight ports for a total power
consumption of 65 W, while at the same time furnishing standard 10/100
Mbps Ethernet functionality.
The AT-GS900/8POE 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 65 watts,
as described in Table 5.