3Com 3CRWE915075 - AirConnect 9150 11n 2.4 GHz PoE Access..., User Manual, Page: 15 / 83

Key Product Features 11
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Providing access to hot spots in public spaces such as coffee
shops or university cafeterias.
IEEE 802.3af
The IEEE 802.3af-2003 Power over Ethernet (PoE) standard
defines terminology to describe a port that acts as a power
source (PSE) to a powered device (PD). The IEEE 802.3af standard
states that power may be delivered by an end-point PSE, using
either the active data wires of an Ethernet port or the spare
wires, to a powered device. An end-point PSE, such as a Power
over Ethernet capable Ethernet switch, may implement either
scheme. If a mid-span PSE is used, then the mid-span PSE can
only implement power delivery over the spare pairs of the copper
cabling and cannot be used to deliver PoE over 1000BASE-T
connections. It should be noted that even if a device supports
both methods of providing power, only one mechanism may be
used to deliver power to a powered device.
The first mechanism is to use the data pairs (pins 1, 2 & 3, 6) to
transmit power, which is sometimes referred to as "phantom"
power. The second power delivery mechanism is to use the
unused, from a 10/100BASE-T perspective, pairs (pins 4, 5 & 7,
8) to deliver power that is supported within mid-span power
delivery.