Allied Telesis AT-PC232/POE - Manual (Page 25)

AT-PC232/POE Media Converter Installation Guide
25
Power Budgeting The AT-PC232/POE Media Converter can provide a maximum of 15.4 W
of power on its twisted pair port (Port 2), along with standard 10/100 Mbps
Ethernet functionality.
The AT-PC232/POE Media Converter smart power management
functionality supports all of the IEEE 802.3af powered device classes
listed in Table 2.
If the twisted pair port is connected to a network node that is not a
powered device (that is, a device that receives its power from another
power source), the port functions as a regular Ethernet port, without PoE.
The PoE feature remains enabled on the port but no power is delivered to
the device.
Implementation
A standard Ethernet twisted pair cable contains four pairs of strands for a
total of eight strands. 10/100 Mbps network traffic requires only four
strands (1, 2, 3, and 6), leaving four strands in the cable unused (4, 5, 7,
and 8).
The PoE standard, IEEE 802.3af, describes two alternative ways for
delivering power to a powered device (PD) over twisted pair cabling.
Alternative A uses the same strands that carry the network traffic.
Alternative B uses the spare strands. The PoE implementation on the AT-
PC232/POE Media Converter is Alternative A, where power is transmitted
over strands 1, 2, 3, and 6.
PD’s that comply with the IEEE 802.3af standard typically support both
power delivery methods. So long as a PD is compliant with the standard, it
should be able to receive its power from the media converter while using
either a straight or cross-over cable. The PoE feature on the AT-PC232/
POE Media Converter should also work with most legacy PD’s as long as
the device can be powered on pins 1, 2, 3, and 6.
Table 2. IEEE 802.3af Class vs. Power Levels
Class Usage
Minimum Power
Levels Output at
the PSE
Maximum Power
Levels Output at
the PD
0 Default 15.4W 0.44W to 12.95W
1 Optional 4.0W 0.44W to 3.84W
2 Optional 7.0W 3.84W to 6.49W
3 Optional 15.4W 6.49W to 12.95W