Enterasys Networks Enterasys SecureStack A2 A2H124-48P - Manual (Page 24)

PoE (Power over Ethernet) Support
1-4 Introduction
Stack Connections
The switches have front‐panel RJ45 connectors for connections in a stack configuration.
The stacking cables used for the connections are standard Category 5 or better UTP cable.
Redundant Power Supply Capability
The SecureStack A2 has power supply redundancy capability when connected to an
optional external redundant power supply (RPS). If the internal power supply fails, the
RPS assumes the entire load of the SecureStack A2 without interrupting network traffic.
The internal power supply and RPS each have their own AC power connection, which
enables the connection of each power supply to a different AC power circuit for
additional AC power source redundancy.
PoE (Power over Ethernet) Support
The switch is 802.3af compliant, which means it can provide power over Ethernet cable
connections from its RJ45 front panel connectors to PDs (powered devices) in the network.
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‐2003
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. The switch can
provide up to 360 watts of PoE power and is capable of supplying a maximum of 15.4
watts to any 10/100 port. In addition it is capable of providing 7.5 watts of power to all
ports simultaneously.
Each PD has a PDC (Powered Device Classification) that is transmitted to the switch for
power management purposes. Table 1‐1 lists the classifications and the associated power
ranges.