The data pairs are used. Since Ethernet pairs are transformer coupled at each
end, it is possible to apply DC power to the center tap of the isolation transformer
without upsetting the data transfer. In this mode of operation the pair on pins 3
and 6 and the pair on pins 1 and 2 can be of either polarity.
POWER SOURCING
EQUIPMENT (PSE)
+ / -
+ / -
48V
4
5
SPARE PAIR
1
TX
2
SIGNAL PAIR
3
RX
6
SIGNAL PAIR
7
8
SPARE PAIR
Figure 2 - Power Supplied over the Data Pins
POWERED DEVICE
(PD)
4
5
1
RX
2
DC / DC
3
Converter
TX
6
7
8
19