Poe (Power Over Ethernet) - TRENDnet TI-PG541i User Manual

TRENDnet User's Guide

PoE (Power over Ethernet)

Power over Ethernet or PoE technology describes a system to pass electrical power
safely, along with data, on Ethernet cabling. PoE requires category 5 cable or higher for
high power levels, but can operate with category 3 cable for low power levels. Power can
come from a power supply within a PoE-enabled networking device such as an Ethernet
switch or can be injected into a cable run with a midspan power supply.
The original IEEE 802.3af-2003 PoE standard provides up to 15.4 W of DC power
(minimum 44 V DC and 350 mA) to each device. Only 12.95 W is assured to be available
at the powered device as some power is dissipated in the cable.
The updated IEEE 802.3at-2009 PoE standard also known as PoE+ or PoE plus, provides
up to 25.5 W of power. Some vendors have announced products that claim to comply
with the 802.3at standard and offer up to 51 W of power over a single cable by utilizing
all four pairs in the Cat.5 cable. Numerous non-standard schemes had been used prior to
PoE standardization to provide power over Ethernet cabling. Some are still in active use.
PSE: Power sourcing equipment (PSE) is a device such as a switch that provides ("sources")
power on the Ethernet cable.
PD: A powered device (PD) is a device such as an access point or a switch, that supports
PoE (Power over Ethernet) so that it can receive power from another device through a
10/100 Mbps Ethernet port.
Standard PoE parameters and comparison
Property 802.3af (802.3at Type 1)
Power
available at 12.95 W
PD
Maximum
15.40 W
power
delivered by
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802.3at Type 2
25.50 W per mode
30.00 W per mode
PSE
Voltage
range (at 44.0 - 57.0 V
PSE)
Voltage
37.0 - 57.0 V
range (at PD)
Maximum
350 mA
current
Maximum
cable 20 Ω (Category 3)
resistance
Power Three power class levels
management negotiated at initial connection
Dreading of
maximum
cable
None
ambient
operating
temperature
Supported
Category 3 and Category 5
cabling
Supported Mode A (endspan), Mode B
modes (midspan)
TI-PG541i
50.0 - 57.0 V
42.5 - 57.0 V
600 mA per mode
12.5 Ω (Category 5)
Four power class levels negotiated at
initial connection or 0.1 W steps
negotiated continuously
5°C with one mode (two pairs) active,
10°C with two modes (four pairs)
simultaneously active
Category 5
Mode A, Mode B, Mode A and Mode B
operating simultaneously
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