Allied Telesis IE200 Series - Manual (Page 28)

Chapter 1: Overview
AT-IE200 Series Installation Guide 28
Critical level are already receiving power. If there is not enough power to support all of the ports set to the
High priority level, power is provided to the ports based on port number, in ascending order.
The lowest priority level is Low. This is the default setting. Ports set to this level only receive power if all of
the ports assigned to the other two levels are already receiving power. As with the other levels, if there is not
enough power to support all of the ports set to the Low priority level, power is provided to the ports based
on port number, in ascending order.
Power allocation is dynamic. Ports supplying power to powered devices may cease power transmission if the
switch’s power budget is at maximum usage and new powered devices, connected to ports with higher
priorities, become active.
Wiring Implementation
The IEEE 802.3af standard defines two methods by which a PSE, such as the switch, can transmit DC power
over twisted pair cables to PDs. These methods, known as modes A and B, identify the wire strands the
switch should use when sending DC power to a PD.
Twisted pair cabling typically consists of eight strands. With 10Base-T and 100Base-T devices, the strands
connected to pins 1, 2, 3, and 6 on the RJ-45 connectors carry the network traffic while strands connected to
pins 4, 5, 7, and 8 are unused. With 1000Base-T devices, all eight strands are used to carry network data.
It takes four strands to deliver DC power to a PD. With Mode A, the power is delivered on pins 1, 2, 3, and
6. These are the same pins in 10Base-T and 100Base-T devices that carry the network data. With mode B,
the power is provided over the spare strands.
The ports on the AT-IE200-6GP and AT-IE200-6FP switches deliver the power using pins 4, 5, 7, and 8, which
corresponds to Mode A in the IEEE 802.3af standard.
Powered devices that comply with the IEEE 802.3af standard are required to support both power delivery
methods. Legacy devices that do not comply with the standard will work with the switch if they are powered
on pins 1, 2, 3, and 6.