Information Technology Reference
In-Depth Information
and patches. Wiring and termination components simply need a fixed mounting
location, wire management devices, and accessibility.
The hubs and other equipment need power, ventilation, and connectivity to
their respective station links. The wiring components tend to be fixed in place for
the life of the installation. The equipment components, however, may need room to
grow and to be reconfigured as network needs change and as technology changes.
The best location for the equipment is one that places the hubs and the wiring
components as close together as practical, while maintaining a logical separation of
the two functions. Remember, too, that some expandability of horizontal wiring
connections should be allowed, and that correspondingly more room should be
allowed for future changes in equipment technology.
In a small installation of less than 100 station terminations, you have a choice
of wall or rack mounting for both the equipment and the cable terminations. There
are advantages (and disadvantages) to both. Wall mounting will give you the most
free and open space in the center of a small wiring closet. However, it limits access
and cable routing options for the wiring components, and wall mounting of hubs
and other equipment may be difficult. Rack mounting may be used both for wiring
components and for hubs, but you will have added expense for the rack, cable trays,
and other accessories.
In larger installations, serious consideration should be given to rack-mounting
all components. This is particularly appropriate with the wide range of wire man-
agement devices for cable racks. You may face an interesting dilemma trying to
decide in which racks to put the hubs. Should they be in the same racks, or should
they be in adjacent racks?
While there may be a certain logic to separating the wiring termination blocks
and patches from the hubs, remember that you must generally run lots of patch
cords between the two. With separate racks, all those patch cords would have to
pass up through one rack and across and down into the other rack to make connec-
tions. Not only is such a long run probably unnecessary, but it may stretch you to
the limit for the channel link. Remember that you are allowed only 10 m (33 ft) for
all equipment cords in a channel, including both the user cords in the work area and
the patch/equipment cords in the TR.
2
If you required a 5-m (16-ft) equipment cord to reach to the hub rack, you
would only have a 5-m (16-ft) allowance in the work area. It is not unusual for
larger work area offices to need 6- to 8-m (18- to 25-ft) user cords, so you would
be better off using as short a TR equipment cord as possible.
2
TIA/EIA-568-B actually now limits the total to 5 m (16 ft) for user cords in the work area, and 5 m
(16 ft) for all equipment cords, patch cords, and cross-connect jumpers in the telecommunications room.
