This MIB is intended for devices powered by
external power sources, in particular Power
Over Ethernet (PoE or formerly called inline
power), to provide power usage configuration
and information for NMS. For example, PoE
supplies DC power over standard Category 5
unshielded twisted-pair (UTP) cable. Instead
of requiring wall power, powered devices such
as IP telephones can utilize power provided
from power source equipments. By using Cisco
Discovery Protocol (CDP), powered devices
can negotiated with power source equipment to
obtain optimum power supply.
The midspan PSE sends out a signal tone down
one of the unused pairs of the standard
Category 5 cable and detects tone on the
other unused pair when the PD loops this tone
back to it through a loopback transformer.
Once the midspan PSE detects this tone, it
begins to provide power down the cable using
the unused pairs. The midspan PSE provide no
physical layer capability.
Powered Device ( PD )
These are devices powered by external electrical
power sources. They are, for example, IP
telephones and wireless Access Points or bridges.
Power Source Equipment ( PSE )
These are devices supplying electrical power to
other equipments. They are, for example, inline
power switches and power patch panels.