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There
are two basic components in an IEEE 802.3af compliant
PoE network: the
Power Sourcing Equipment and the Powered Device.
•
Power Sourcing Equipment (PSE)
A
device that supplies power
•
Powered Device (PD)
A
device that receives and utilizes the power
Upon
supply of power, the PSE starts with detecting the
connected devices and verifies if it’s a PoE enabled
device. It
sends out 2 different short low voltage discovery
signals between 2.7V and 10.1V with at least 2ms in
between. For
a PoE enabled device, it has a built-in 25k ohm resistor
which when detected by the PSE, identifies itself as PoE
enabled device. PSE
will supply 48V and a max. current of 350mA.
Voltage may be lost depending on the distance;
however, a min. of about 13W is delivered to each
powered device, which is adequate for numerous
applications. PoE
connections can reach a max. of
100m
(328 feet).
PSE
will constantly monitor the device.
Once the powered device’s current consumption
drops below a min. value, for example it is removed; the
PSE unit will discontinue supplying power and the
process for powered device detection begins again. |
