User's Manual

AT-GS900/8PS Switch Installation Guide
29
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 Alternatives A and B, identify the wire strands the
switch should use when sending DC power to a PD. The AT-GS900/8PS
switch delivers power using Alternative A.
Twisted pair cabling typically consists of eight strands. With 10Base-T and
100Base-TX 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 Alternative A, the
power is delivered on pins 1, 2, 3, and 6. With Alternative B, the power is
provided over the strands connected to pins 4, 5, 7, and 8.
The ports on the AT-GS900/8PS switch delivers the power using pins 1, 2,
3, and 6, which corresponds to Alternative A in the IEEE 802.3af standard.