|
TIA/EIA-568-A specifies
that when using an Ethernet star topology, every device that is part of the
network must be connected to the hub by a run of horizontal cabling. 
The central point of
the star topology, where the hub is located, is called the wiring closet.
It helps to think of the hub as the center point of a circle which has
lines of horizontal cabling radiating from it, like spokes from the center
of a wheel. 
In order to determine
the location of a wiring closet, begin by drawing a floor plan of
the building (approximately to scale), and adding to it all of the devices
that will be connected to the network. As you do this, remember that
computers are not the only devices that you will want to connect to the
network; there are also printers and file servers to consider.
When you have completed
this process, you should have a floor plan that is similar to the one shown
in the Figure  .
Horizontal Cabling
System Structure
The horizontal cabling system extends from the telecommunications outlet in
the work area to the horizontal cross-connect in the telecommunications
closet. It includes the telecommunications outlet, an optional consolidation
pointer transition point connector (horizontal cable, and the mechanical
terminations and patch cords or jumpers) that comprise the horizontal
cross-connect. 
Some points specified
for the horizontal cabling subsystem include:
·
Recognized
Horizontal Cables: 
·
4-pair100
Ω UTP
·
2
fiber (duplex) 62.5/125 µm or multimode optical fiber (note: 50/125 µm
multimode fiber will be allowed in ANSI/TIA/EIA-568-B)
Note: ISO/IEC 11801are 120 Ω UTP and 50/125 µm multimode
optical fiber.
·
Multipair
and multi-unit cables are allowed, provided that they satisfy the hybrid
bundled cable requirements of TIA/EIA-568-A-3.
·
Grounding
must conform to applicable building codes, as well as ANSI/TIA/EIA-697.
·
A
minimum of two telecommunication outlets are required for each individual
work area.
·
First
outlet: 100 Ω UTP (Cat 5e recommended).
·
Second
outlet: 100 Ω UTP (Cat 5e recommended).
·
Two-fiber
multimode optical fiber either 62.5/125 µm or 50/ 125 µm.
·
One
transition point (TP) is allowed between different forms of the same cable
type (i.e. where undercarpet cable connects to round cable).
Note: The definition provided for a “transition point” on ISO/IEC
11801 broader than '568-A. It includes transitions to under carpet cabling
as well as consolidations point connections.
·
50
Ω coax and 150 Ω STP-a cabling is not recommended for new
installations.
·
Additional
outlets may be provided. These outlets are in addition to and may not
replace the minimum requirements of the standard.
·
Bridged
taps and splices are not allowed for copper-based horizontal cabling.
(Splices are allowed for fiber.)
Note: In ISO/IEC 11801, the equivalent cabling element to the
horizontal cross-connect (HC) is called the floor distributor (FD).
·
Application
specific components shall not be installed as part of the horizontal
cabling. When needed, they must be placed external to the
telecommunications outlet or horizontal cross-connect (eg. Splitters,
baluns).
·
The
proximity of horizontal cabling to sources of electromagnetic interference
(EMI) shall be taken into account. 
|
