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Twisted Pair Cables for 100 BASE-TX
For two devices to communicate, the transmitter of each device must be connected
to the receiver of the other device.The crossover function is usually implemented
internally as part of the circuitry in the device. Computers and workstation adapter
cards are usually media-dependent interface ports, called MDI or uplink ports.
Most repeaters and switch ports are configured as media-dependent interfaces with
built-in crossover ports, called MDI-X or normal ports.
Auto Uplink
TM
automatically senses which connection, MDI or MDI-X, is needed and
makes the right connection.
Figure C-1 illustrates straight-through twisted pair cable.
1
Tx
2
A
3
Rx
6
Key:
A = Uplink or MDI port (as on a PC)
B = Normal or MDI-X port (as on a hub or switch)
1, 2, 3, 6 = Pin numbers
Figure C-1.
Straight-Through Twisted Pair Cable
Figure C-2 illustrates crossover twisted pair cable.
1
Rx
2
B
3
Tx
6
Ke
y:
B = Normal or MDI-X port (as on a hub or switch)
1, 2, 3, 6 = Pin numbers
Figure C-2. Crossover Twisted Pair Cable
1
Rx
2
B
3
Tx
6
1
Rx
2
B
3
Tx
6
cabling guidelines
C-5
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