Information Technology Reference
In-Depth Information
cable into modular plugs may be outside the ability of the average cable technician,
because of the narrow tolerance in placement of the conductors in the plug. If you
must trim to length, follow the methods in Chapter 9 for terminating the cable.
If you use manufactured cables, the excess must either be stored in the work
area or in the MUTOA location. One possible storage method is to use one of the
cable management devices to store the excess cord length. These can be slotted race-
ways, a series of cable management rings or standoffs, or one of the snap-in-place
patch cable management devices. In general, any device that could be used in the TR
to manage patch cables can be used here.
Horizontal Distances for the MUTOA Method.
The formula for this calculation
is given in the standard, but the maximum horizontal runs for several lengths of
work area cable are shown in Table 10.1. As you can see, the length of work area
cord is the normal 5-m length at the maximum horizontal distance of 90 m. This is
a total of 95 m and, when added to the cross-connect/equipment cable length of 5
m, yields the magic total of 100 m, on which most of our LAN topologies are based.
However, at the maximum user cord length of 20 m, only 70 m of horizontal cable
is allowed (rather than the expected 75 m), which is to compensate for the poorer
transmission parameters of stranded-wire cables.
The total length allowed for the channel in open-office wiring is always at or
below the length in normal horizontal links. In testing a link that uses the consoli-
dation point method, the normal tests for basic link and channel are still completely
valid. However, if you use the multiuser outlet method, the differences in the allow-
able horizontal run and in the user cord lengths are significant. You should do a pre-
liminary check of the run of the MUTOA in accordance with the basic link test
parameters, but you should allow an extended “pass” margin to compensate for the
slightly poorer performance of the extended user cord, which is excluded from the
basic link.
In the end, you really must check the entire channel link, as that is the ultimate
connection path on which the high-speed network must operate. If equipment and
TABLE 10.1
Horizontal Distances versus Work Area Cable Lengths for MUTOA
Work area cable
Horizontal cable
5 m (16 ft)
90 m (295 ft)
11 m (36 ft)
80 m (262 ft)
20 m (66 ft)*
70 m (230 ft)
*This is the maximum length for work area cords.
