Powered Device Classifications (Pds) - Enterasys D2G124-12 Hardware Installation Manual

Power over Ethernet (PoE) refers to the ability to provide 48 Vdc power to a powered device using
the same Ethernet cabling that provides data. Modern Ethernet implementations employ
differential signals over twisted pair cables. This requires a minimum of two twisted pairs for a
single physical link. Both ends of the cable are isolated with transformers blocking any DC or
common mode voltage on the signal pair. PoE exploits this fact by using two twisted pairs as the
two conductors to supply a direct current. One pair carries the power supply current and the other
pair provides a path for the return current. While several proprietary legacy implementations of
PoE have been deployed by LAN equipment vendors, in 2003 the IEEE published the IEEE 802.3af
specification, which is part of the 802.3 suite of standards.
The switch is fully compliant with the IEEE 802.3af standard. It supports the standard
resistor‐based detection method, as well as AC disconnect capability.
When operating at 40°C or less, the switch supports an average of 8.3W PoE power per port. It
provides up to 15.4W for Class 3 support on any port, up to a system maximum of 100 watts. Total
system PoE power decreases 2.16W per °C increase over 40°C.

Powered Device Classifications (PDs)

PDs are devices that receive their operating 48 Vdc power through a new or existing Ethernet
cable from a switch or other device that can provide a PoE‐compliant port connection. This
enables the PD to operate in a location without local power. For example:
• Devices such as PoE‐compliant remote EXIT signs and Personal Data Assistants (PDAs),
• Devices that support Voice over IP such as PoE‐compliant digital telephones,
• Devices that support Wireless Application Protocol (WAP) such as security cameras, laptop
PCs, and many more devices.
PoE (Power over Ethernet) Support
Enterasys D-Series Hardware Installation Guide 1-5