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Chapter 8
Power Over Ethernet
Overview
What is PoE?
Based on the global standard IEEE 802.3af, PoE is a technology for wired Ethernet, the
most widely installed local area network technology adopted today. PoE allows the
electrical power necessary for the operation of each end-device to be carried by data
cables rather than by separate power cords. New network applications, such as IP
Cameras, VoIP Phones, and Wireless Networking, can help enterprises improve
productivity. It minimizes wires that must be used to install the network for offering
lower cost, and less power failures.
IEEE802.3af also called Data Terminal equipment (DTE) power via Media dependent
interface (MDI) is an international standard to define the transmission for power over
Ethernet. The 802.3af is delivering 48V power over RJ-45 wiring. Besides 802.3af also
define two types of source equipment: Mid-Span and End-Span.
• Mid-Span
Mid-Span device is placed between legacy switch and the powered device. Mid-Span
is tap the unused wire pairs 4/5 and 7/8 to carry power, the other four is for data
transmit.
• End-Span
End-Span device is direct connecting with power device. End-Span could also tap the
wire 1/2 and 3/6.
GE-DS-82 and 82-PoE Ethernet Managed Switch User Manual
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