3Com 3CRWE915075 User Guide - Page 15

IEEE 802.3af, The IEEE 802.3af-2003 Power over Ethernet PoE standard

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Key Product Features 11 ■ 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.

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Key Product Features
11
■
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.