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AT-30xxTR Multiport Repeaters
25
UTP MAU-to-MAU,
Hub-to-Hub Wiring
10BASE-T MAU-to-MAU or hub-to-hub wiring generally requires a
crossover cable located somewhere along the UTP cable run. This may
commonly occur at the punch-down block or between the RJ45 wall
receptacle and the workstation. See Figure 20.
MDI/MDI-X
Switch
The AT-30xxTR additionally has an MDI/MDI-X pin-out switch that affects
RJ45 Port #1. The RJ45 pin-out straight-through (MDI)/crossover (MDI-X)
switch enables you to use a straight-through cable (see Figure 19 above)
during hub-to-hub connectivity by simply placing the switch in the MDI
position. This eliminates the need for making or obtaining a crossover cable,
as shown in Figure 20.
The interface type that IEEE specifies as standard for a repeater such as the
AT-30xxTR is MDI-X. The straight-through/crossover switch merely
provides convenience to avoid having to obtain an alternate cable in some
applications. If you connect a cable and it does not work, try changing the MDI
switch. The rule of thumb is the total number of crossovers must be odd. You
cannot harm the repeater by having the MDI switch in the wrong position.
Figure 19: RJ45 Cable
Pin 1
Figure 20: Hub-to-Hub or
MAU-to-MAU Wiring
Not Used
RD-
Not Used
Not Used
RD+
TD-
TD+
Not Used
Not Used
RD-
Not Used
Not Used
RD+
TD-
TD+
Not Used
RJ 45 Pin
RJ 45 Pin
1
2
3
4
5
6
7
8
1
2
3
4
5
6
7
8
Pair twisted as per level 3, 4 or 5 cable
1
1
1
Note