Digimerge DNP5220E, Руководство по оборудованию

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Appendix #5 - Power Over Ethernet (PoE)
SECTION 5
Appendix #5 - Power Over Ethernet (PoE)
Power over Ethernet, also known as PoE, is a technology for carrying power along with data on
standard CAT5 network cables, allowing devices to be powered via their network ports. It is sup-
ported by some devices directly (e.g. 802.3af compliant or “PoE Enabled” devices) while other
devices require PoE accessories, such as PoE Endspans, PoE Midspans, power injectors and/or
active splitters, in order to make use of the technology.
• PoE Endspan – PoE enabled Ethernet switch
• PoE Midspan - PoE multi port injector for use with non-PoE Ethernet switches
• PoE Injectors – Adapter that injects Power into an Ethernet cable. Can be used in combination
with an active splitter (for connecting to non-PoE devices) or used on its own (for connecting
to PoE enabled devices)
• Active Splitter – An adapter that splits the Date and Power transmissions over a single
Ethernet cable (PoE) into a separate Date (using RJ45 connector) and power stream (using
power barrel connector) for use strictly with non-PoE devices
NOTE: PoE allows devices to be powered with a power rating of up to 12.9W. Devices that con-
sume more then 12.9W but less than 39W require use of High Power PoE (IEEE-802.3at)
devices. High Power PoE devices like the 8000 series from Microsemi are readily available. An
example of an IP camera that would require High Power PoE to power it up would be PTZ Speed
Dome cameras which consume a lot of power.
A detailed description of the 802.3af standard is available in IEEE publication SS95312
( http://standards.ieee.org/getieee802/download/802.3af-2003.pdf ).
The main benefits of PoE technology are:
Lower Costs
• Eliminate the need to run A/C power wires
• Utilize existing IT infrastructure investments
More Flexible
• Locate device where it truly needs to be located ( Not constrained by the location of an AC outlet)
Centralize vs. Localize Power Source
• Allow use of a centralized UPS (Uninterruptible power supply) to guarantee power to the
device even during a power failure