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Description
3.2 Power over Ethernet (PoE)
3.2
Power over Ethernet (PoE)
Power over Ethernet (PoE)
With PoE, the power for networked devices is carried via Ethernet. Here, there are two
methods of supplying power:
● Alternative A
Here, the voltage is transferred on the data wires 1, 2, 3 and 6 of the Ethernet cable
Requirements for the Ethernet cable:
– For 10Base-T/100Base-TX, a 4-wire cable is adequate for data transmission and
– With 1000BASE-T, an 8-wire cable is necessary for data transmission.
● Alternative B
Power is transferred on the free wires 4, 5, 7 and 8 of the Ethernet cable.
Requirements for the Ethernet cable: For 10Base-T/100Base-TX/1000BASE-T, an 8-wire
cable is needed.
PoE-compliant devices can be divided into the following groups:
● PSE - power sourcing equipment
These inject power onto the Ethernet cable.
● PD - powered devices
These are supplied with power via Ethernet.
The PoE ports of the switch
As a PSE, the X308-2M PoE supplies PoE-compliant devices with power over Ethernet. The
48 V power required to supply the powered devices is generated internally on the switch, no
extra power supply unit is necessary.
The X308-2M PoE uses the "alternative A" for this. Per RJ-45 port, a maximum of 15.4 W
are available for supplying a PoE-compliant device. If a Cat5/Cat5e cable with a maximum
length of 100 m is used, the connected device can be supplied with a power of 12.95 W.
Note
The total power provided by the SCALANCE X308-2M PoE on all four PoE ports is a
maximum of 30.8 W.
The PoE ports meet the conditions listed in the IEEE 802.3af / IEEE 802.3at standard
(type 1) for environment A , in other words power supply over Ethernet within a power supply
system. For details of configuring and enabling PoE for individual ports, refer to the
configuration manual SCALANCE X-300 / X-400 on the accompanying CD.
14
power supply.
Compact Operating Instructions, 05/2016, A5E02630810-09
SCALANCE X-300M PoE
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