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Chapter 1: Overview
Wiring
Implementation
40
The IEEE 802.3af standard defines two methods for delivering DC power
over twisted pair cable by a switch to powered devices. These methods
are known as Modes A and B, and identify the individual wires that carry
the DC power within the cable from the switch to powered devices.
Twisted pair cabling typically consists of eight wires. With 100Base-TX
devices, the wires connected to pins 1, 2, 3, and 6 on the RJ-45
connectors carry the network traffic while the wires connected to pins 4, 5,
7, and 8 are unused. At higher speeds, all eight wires are used to carry
network data.
It takes four wires to deliver DC power to a powered device. With Mode A,
power is delivered on pins 1, 2, 3, and 6. These are the same pins in
10Base-T and 100Base-TX devices that carry the network data. With
Mode B, power is provided over the spare wires.
The PoE wiring modes of the twisted pair ports on the x530DP Switches
are as follows:
Classes 0-4 (Types 1 and 2 up to 30W) Mode A (MDI-x)
Classes 5-6 (Type 3 up to 45W/60W) Mode A (MDI-x) plus Mode B
(MDI-x, MDI)
Powered devices of classes 0 to 4 that comply with the IEEE 802.3af
standard are required to support both Modes A and B. Legacy devices that
do not comply with the standard will work with the switch if they are
powered on pins 1, 2, 3, and 6.
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