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wired LAN. Using a Power-over-Ethernet system, installers need to run only a single
Category 5 Ethernet cable that carries both power and data to each device. This allows
greater flexibility in the locating of network devices and, in many cases, significantly
There are two system components in PoE - the PSE (Power Sourcing Equipment) and
the PD (Powered Device). The IEEE 802.3af/at specification defines PSE as a device that
inserts power onto an Ethernet cable. The PSE may be located at the switch (Endspan
configuration). or it may be a separate device located between the switch and the PD
(Midspan configuration). The PD is the natural termination of this link, receiving the power,
and could be an IP phone, a WLAN access point, or any other IP device that requies
power. The current is transmitted over two of the four twisted pairs of wires in a
Category-5 cable.
Power-over-Ethernet follows the IEEE 802.3af/at specification and is completely compatible
with existing Ethernet switches and networked devices. Because the Power Sourcing
Equipment (PSE) tests whether a networked device is PoE-capable, power is never
transmitted unless a Powered Device is at the other end of the cable. It also continues to
monitor the channel. If the Powered Device does not draw a minimum current, because it
has been unplugged or physically turned off, the PSE shuts down the power to that port.
Optionally, the standard permits Powered Devices to signal th the PSEs exactly how
much power they need.
Unicom’s Micro-SwitchPoE/5
Switch is a multi-port switch that can be used to build
high-performance switched workgroup networks. This switch is a store-and-forward
device that offers low latency for high-speed networking. It also features a
“store-and-forward” switching scheme that allows the switch to auto-learn and store
source addresses in a 1K-entry MAC address table. The switch is targeted at workgroup,
department or backbone computing environments.
decreases installation costs.
Introduction
Power-over-Ethernet (PoE)
eliminates the need to run DC power to other devices on a
