Data Cabling Techniques
14
Table 2 shows which position the straight-through/crossover selection switch
needs to be for the device configuration shown.
Table 2:
MDI and MDI-X Switch Settings for Common Connection
1
In both the crossover and straight-through instances, the wire is twisted pair.
Figure 12 demonstrates usable and unusable cable configurations for the
straight-through wire pairing in the UTP environment.
Diagram A is correct because the proper pairs are twisted together.
Diagram B is incorrect because the wires for the receive pair, pins 3 and 6, are
not twisted together. This could result in excessive common mode noise and
an unacceptably high data error rate.
Model
Connected to
MDI
MDI-X
AT-4016TR
Hub
X
AT-4016TR
RJ45 Transceiver
X
AT-4016TR
NIC
X
1. This table assumes a straight-through cable is being used. The switch setting are the opposite of what is
shown if a crossover cable is being used.
Figure 12:
Hub-to-MAU Wiring
(A) Usable and (B) Unusable
Not Used
RD-
Not Used
Not Used
RD+
TD-
TD+
Not Used
Not Used
RD-
Not Used
Not Used
RD+
TD-
TD+
Not Used
RJ45 Pin
RJ45 Pin
1
2
3
4
5
6
7
8
1
2
3
4
5
6
7
8
1
1
Pair twisted as per Level 3, 4 or 5 cable.
1
A
Not Used
RD-
Not Used
Not Used
RD+
TD-
TD+
Not Used
Not Used
RD-
Not Used
Not Used
RD+
TD-
TD+
Not Used
RJ45 Pin
RJ45 Pin
1
2
3
4
5
6
7
8
1
2
3
4
5
6
7
8
This cable will not work for 10BASE-T.
Note that 3 and 6 are twisted, but are not a pair.
B
