4 HORIZONTAL CABLING
The horizontal cabling is the portion of the telecommunications cabling system that extends from the
work area telecommunications outlet/connector to the horizontal cross-connect in the
telecommunications room. The horizontal cabling includes horizontal cables, telecommunications
outlet/connectors in the work area, mechanical terminations, and patch cords orjumpers located in the
telecommunications room, and may include multi-user telecommunications outlet assemblies and
NOTE - The term "horizontal" is used since typically the cable in this part of the cabling
system runs horizontally along the floor(s) or ceiling(s) of a building.
The following list of common services and systems should be considered when the horizontalcabling is
designed. (The list is not intended to be complete.)
a) Voice telecommunications service
b) Premises switching equipment
c) Data communications
d) Local area networks (LAN)
f) Other building signaling systems (building automation systems such as fire, security, HVAC,
In addition to satisfying today's telecommunications requirements, the horizontal cablingshould be
planned to reduce on-going maintenance and relocation. It should also accommodate future equipment
and service changes. After construction of the building, the horizontal cabling is often much less
accessible than the backbone cabling. The time, effort, and skills required for changes can be
extremely high. In addition, access to the horizontal cabling frequently causes disruption tooccupants
and their work. These factors make the choice and layout of horizontal cable types very important to
the design of the building cabling. Consideration should be given to accommodating a diversity of user
applications in order to reduce or eliminate the probability of requiring changes to the horizontal cabling
as user needs evolve.
The pathways and spaces shall be designed andinstalled to support horizontal cabling in accordance
with the requirements of ANSI/TIA/EIA-569-A.
The horizontal cabling shall be installed in a star topology as shown in figure 4-1. Each work area
telecommunications outlet/connector shall be connected to a horizontal cross-connect in a
telecommunications room via the horizontal cable. A telecommunications room should be locatedon
the same floor as the work areas served.
Some networks or services require applications-specific electrical components (such as impedance
matching devices). These application-specific electrical components shall not be installed as part of the
horizontal cabling. When needed, such electrical components shall be placed external to the
telecommunications outlet/connector. Keepingapplication-specific components external to the
telecommunications outlet/connector will facilitate the use of the horizontal cabling for varying network
and service requirements.
Horizontal cabling shall contain no more than one transition point or consolidation point between the
horizontal cross-connect and telecommunications outlet.
Bridged taps and splices shall not beinstalled as part of the copper horizontal cabling. Splitters shall
not be installed as part of the optical fiber horizontal cabling.
1 – Cabling between telecommunications rooms for the purpose of creating "bus" and
"ring" topologies is considered part of the backbone cabling. The direct connections
between nearby telecommunications rooms are covered in subclause 5.2.3.
2 – Centralizedoptical fiber cabling is designed as an alternative to the optical
cross-connection located in the telecommunications room when deploying recognized
optical fiber cable in the horizontal in support of centralized electronics. Specifications
concerning centralized cabling are found in annex A.
Figure 4-1 Typical horizontal and work area cabling using a star topology
4.3 Horizontal distances
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