19
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)
POWERED DEVICE
(PD)
SPARE PAIR
SPARE PAIR
SIGNAL PAIR
SIGNAL PAIR
DC / DC
RX
TX
TX
RX
48V
4
5
1
2
3
6
7
8
4
5
1
2
3
6
7
8
+
/
-
+
/
-
Converter
Figure 2
- Power Supplied over the Data Pins
