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User Manual – DANTE
TM
Adapter NA2-IO-DPRO | BDA 573 V1 2019/08
Appendix
7.2 PoE (Power over Ethernet)
PoE stands for Power over Ethernet and describes a practice for using a single CAT5e (or higher) to
incorporate both power and data in the single cable.
Few advantages:
•
Easy setup
•
Single cable run up to 100 m
•
Using PoE doesn’t require certified electrician as the power loads are small
•
Existing network infrastructure can be used
7.2.1 Definitions
PD
(Powered device) – device that is connected to PSE and thus is powered by it.
PSE
(Power Sourcing Equipment) – device that provides power to PD, Switch or injector
PSE Types
In our case, we consider only following two types of PSE devices.
•
PoE Switch: a switch that offers possibility to power PD. Switches use PoE classification.
•
PoE Injector: typically a single port device for powering 1 PD. These exist with classification
(active) or without (passive).
The term class refers to a maximal power output (see table below).
7.2.2 PoE Standards
These standards are part of IEEE 802.3 general standards.
802.3 af – defines PoE classes 0-3
802.3 at – uses the same classes, but introduces class 4 as well.
7.2.3 Classes and discovery process
Discovery is a process of PSE, determining the power requirements of the PD. Once PD and PSE are
connected, PSE sends out a short voltage impulse, reads the returned value and provides power
accordingly. This is valid for PSE with class (also called active).
No class (passive) PSE, acts as a classic power supply, hence no discovery is implemented, and PSE
supplies current at all times.
Class
Type
Power required by PoE class at the Powered Device (PD)w
1
802.3af
0.44 - 3.84 W
2
802.3af
3.84 - 6.49 W
3
802.3af
6.49 - 12.95 W
4
802.3at PoE+
12.95 - 25.5 W
