|  | 8.3 |

Planning Structured Cabling: Identifying Potential Wiring Closets

| 8.3.1 | Topology as floor plan

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.

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