Information Technology Reference
In-Depth Information
In reality, the total length of each horizontal link is the real operating limit of
a LAN circuit. This limit is 100 m (328 ft) for the entire Channel, including all of
the cables, cords, and jumpers that run all the way from the back of the worksta-
tion to the network hub. The 100 m (328 ft) includes 10 m (33 ft) for all the cords
and jumpers, with the understanding that the stranded wires used in these cords
have a 20% greater attenuation.
Although the standard requires that all horizontal cables be solid wire, you
could safely exceed the 10-m (33 ft) limit for user cords and jumpers by a little bit
if you were well below the 90-m (295 ft) limit for the horizontal cable.
User cords in the work area should be routed with the same guidelines as for
the horizontal cable runs. You should avoid sharp bends, kinks, and abrasions of
the cable, and you should route it away from potential interference sources, such as
fluorescent lights and motors.
Modular furniture usually requires that user cords be placed in raceways that
are built into the furniture. Remember that the guidelines suggest a separation of 2
to 5 in from power conductors, such as the AC outlets (or mains) in the furniture
channels. Furniture manufacturers are beginning to recognize the need for totally
separate telecommunications raceways, so you may be able to specify furniture that
meets this requirement. The placement of Category 5e and 6 cable is much more
sensitive than lower categories. If you are still operating a 10BaseT or Token-Ring
16 network, you really do not need Category 5 performance, and you may want to
relax the rules somewhat. Routing of user cables in the telecommunications room
will not be covered here, as it is identical to patch cord routing, which was covered
in Chapters 6 and 7.
Workmanship and Quality
If you build your own user cords, or if you manufacture them for others, the qual-
ity of construction is a very important factor in the performance of the cord. You
should first ensure that all connectors and cable used in the assembly of the cord are
certified by the manufacturer for the level of performance you desire for the com-
pleted cord. Then, you should use proper techniques to assemble the cord for max-
imum performance. It is known to be difficult to test short lengths of cable,
particularly with regard to NEXT, so your best performance guarantee is good
workmanship. Basic continuity and wire map, of course, can be completely tested
without regard to length.
The section on patch cords in Chapter 8 and the earlier section on modular
connectors in this chapter describe some techniques to ensure a high-quality termi-
nation that will perform up to expectations.
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