Allied-telesis AT-8550SP User Manual download pdf (Page 23)

AT-8500 Series Fast Ethernet Switch Installation Guide

Power Over Ethernet

The following discussion applies only to the AT-8524POE switch.

The twisted pair ports on the AT-8524POE switch offer the same features

and functionality as the twisted pair ports on the other switches in the

series. As such, they can operate at 10 or 100 Mbps, feature Auto-

Negotiation and Auto-MDI/MDI-X, and so forth.

But they do have an importance difference in that they also 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 to 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, webcams, and even other Ethernet switches. An example

of the latter is the unmanaged AT-FS705PD Ethernet switch from Allied

Telesyn. 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-8524POE

switch adds to the installation and maintenance of your network. First,

since the switch acts as the central power source for your powered

devices, adding a redundant power supply (RPS) or 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 a device connected to a

port is a powered device or not. 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 the device is a powered device.

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Allied-telesis AT-8550SP User Manual Page 23