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Twisted Pair Cables
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. Most ports on
switches and repeaters have media-dependent interfaces with crossover ports.
These ports are referred to as MDI-X or normal ports. Computer and
workstation adapter cards are usually media-dependent interface ports referred
to as MDI or uplink ports.
These two figures illustrate the use of straight-through and crossover twisted
pair cables.
RJ-45 Connector
The RJ-45 connector (shown in the illustration with an RJ-45 plug) is used to
connect workstations, hubs, and switches through unshielded twisted pair cable.
The RJ-45 connector accepts four-pair Category 3 or Category 5 UTP cable.
Only two pairs are used for 10BASE-T wiring.
RJ-45
Connector
Normal Assignment:
Pin
Assignment
1
Input Receive Data +
2
Input Receive Data -
3
Output Transmit Data +
6
Output Transmit Data -
4,5,7,8
Not used
Model FS308 Fast Ethernet Switch Installation Guide
Straight-through
Uplink or
twisted pair cable
MDI port
1
Tx
2
3
Rx
6
Normal or
Crossover
twisted pair cable
MDI-X port
1
Rx
2
3
Tx
6
12345678
Normal or
MDI-X port
1
Rx
2
3
Tx
6
Normal or
MDI-X port
1
Rx
2
3
Tx
6
8146EC
8
1
711EA
Uplink Assignment:
Port 8 on the Model FS308
switch
Output Transmit Data +
Output Transmit Data -
Input Receive Data +
Input Receive Data -
Not used
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