3.6.7 Power over Ethernet (PoE)
This Gateway is equipped with PoE technology to derive its power from another PoE
device via the Ethernet connection (PD mode). This device complies with the IEEE
802.3af-2003 or IEEE 802.3at -2009 for PD operation.
These standards require the use of Category 5 Ethernet cable or higher. In the operation of
IEEE 802.3a, PoE power is only transmitted from one device to another when the proper
impedance match is made. This prevents damage to non PoE devices on the network.
To use this feature, the Gateway must be connected over the Ethernet to a matching IEEE
802.3a device. Failure to do this will cause no power sourced. A switch on the power
supply board allows a PD (Powered Device) to be enabled or disabled.
PoE advantages
To save costs on planning, wiring and installation of networks, devices are supplied with
power directly via the Ethernet cable (e.g. via a Cat 5/5e cable up to 100m). PoE makes the
network planning flexible, independent of power supply cabinets, and junction boxes.
There are no extra costs for the electrical wiring. An advantage of PoE is that you can install
devices with an Ethernet interface in places of difficult access or in areas in which running
cable would be inconvenient. This in turn saves installation time and costs. This
technology is in use today typically in IP telephones, cameras, or wireless transmission
devices such as WLAN Access Points.
An excellent application is a Gateway connected to a Wi-Fi back haul unit; such as a Cisco
®
unit. For example, a Cisco IW6300 unit could power the Gateway over a PoE connection.
Selecting devices to work with a PoE Gateway
When connecting the Gateway to a PSE device, it must be labeled as compliant with IEEE
802.3af or IEEE 802.3at. Many companies use labels on their packaging such as PoE for
IEEE 802.3af or PoE+ for IEEE 802.3at. Check the specific manufacturer's specifications of
any device to make sure somewhere it references IEEE 802.3; otherwise it may not work.
Caution is needed in selecting a companion device to the Gateway for PoE. Not all devices
labeled PoE will function. Before 2003, there was no standard and companies developed
their own techniques for powering over an Ethernet cable. These techniques are not
always interoperable. Before the standard, they used the term PoE on many of their
products. Most new products labeled PoE are IEEE compatible. Cisco products can be
ordered with their old standard (Online Power as it is sometimes referred to) or with the
IEEE 802.3 PoE standard. Check with the appropriate manufacturer if in doubt before
purchasing/installing the connecting equipment.
For reference, Cisco offers the following four versions:
1.
Pre standard PoE (Online Power)
2. 802.3af-compliant PoE (15W)
3. 802.3at-compliant PoE Plus (PoE+) (25W)
4. Universal PoE (UPoE) (60W). (New Cisco standard, which Cisco claims is compatible
with IEEE 802.3af PoE and IEEE 802.3at PoE +)
Reference Manual Installing the Gateway
00809-0600-4410 May 2020
Emerson 1410S/781S 31
To Next Page
Loading...
