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Structured Cabling Installation Practices - Part Two - Structured Cabling

Sub-systems for a Structured Cabling System

Here in part two of our series, we offer an in-depth look at structured cabling and what it is all about.

In the early 1980s, when computers were first linked together in order to exchange information, 
many different cabling designs were used. Some companies built their systems to run over coaxial cables. Others thought that twinaxial or other cables would work best. With these cables, certain parameters had to be followed in order to make the system work. Certain connectors had to be used, maximum cable distances had to be established and particular topologies were necessary.

By defining every aspect of their proprietary system, one manufacturer's system would not work with another, or run over any other type of cabling. If a customer decided to change systems, not only would new electronics and software need to be purchased, but new cabling would need to be installed as well. Moves, additions, changes and troubleshooting were also difficult with a proprietary system. In order to troubleshoot a network, quite often a link would need to be tested meaning disruption to network services. These factors contributed to a growing frustration among network managers and administrators who constantly searched for easier ways to maintain their networks, reduce downtime and lower costs.

Out of this frustration, the idea and design of the Structured Cabling System was born. Structured cabling was designed to run anything, anywhere, at any time, eliminating the need to follow a proprietary topology and allowing for the installation of cabling in a facility once and the adapting of that cabling for any application - from telephone to Ethernet, video or VOIP.

​The Structured Cabling System (SCS) is comprised of a set of cabling and connectivity products that integrates the voice, data, video, and various management systems of a building (such as safety alarms, security access, energy systems etc). It consists of an open architecture, standardized media and layout, standard connection interfaces, adherence to national and international standards, and total system design and installation.

What are the advantages of a Structured Cabling System? 

  • A standardized cabling infrastructure.
  • Flexible cabling scheme, without regard to its ultimate use.
  • Support voice and data (and even video for short distances).
  • Allows easier moves, adds and changes.
  • Upgrades to different network types.
  • Not mandatory, but followed for inter-operability.

Every structured cabling system is unique. This is due to variations in the architectural structure of the building, which houses the cabling installation; the cable and connection products; the function of the cabling installation; the types of equipment the cabling installation will support -- present and future; the configuration of an already installed system (upgrades and retrofits); and customer requirements.

The wiring system of the building can be composed as follows:
Campus Distributor (CD)
Building Distributor (BD)
Floor Distributor (FD)
Consolidation Point (CP)
Telecommunications Outlet (TO)

Structured cabling falls into six sub-systems

1. Entrance Facilities
2. Equipment Rooms
3. Backbone Cabling
4. Telecommunications Rooms
5. Horizontal Cabling
6. Work-Area Components

Entrance Facilities 

Entrance Facilities provide the point at which outside cabling interfaces with the intra-building backbone cabling. The physical requirements of the network interface are defined in the ANSI/TIA-569 standard. The Entrance Facilities typically contain the demarcation point as well as internal and external building to building backbone facilities. As the Entrance Facilities are also used to house backbone cabling, the design and other requirements of this space are handled by pathways and spaces standards.

Entrance Facility Room Requirements 
  • Should be located close to the building entrance point.
  • Lighting to be at a minimum of standard office lighting.
  • Entrance Facility should not have a lowered ceiling.
  • Entry ways should be of adequate size to accommodate equipment.
  • Electrical services should not cause any interference.
  • Should contain dual power in an accessible location.
  • All environmental conditions should be taken into account.

Equipment Rooms

The Equipment Room in a building is a centralized space for telecommunications equipment that serves the occupants of the building.

* It is important to note: An Equipment Room is considered distinct from a Telecommunications Room because it is considered to be a building or campus serving (as opposed to floor serving) facility and because of the nature or complexity of the equipment that it contains. The equipment room usually houses the telecommunication installations that serve the occupants of a building or multiple buildings in a campus environment. It will typically contain the majority of the telecomm-unications equipment, cable terminations, and cross-connects. Equipment Rooms are used to house backbone and horizontal cabling. The requirements that cover design and other functional requirements of Equipment Rooms are provided by the pathways and spaces standards such as ANSI/TIA/EIA-569-B. 

While the Equipment Room will house main and intermediate cross connects for the backbone terminations, it can also house cross-connects for horizontal and demarcation terminations for a portion of the building.

As the room houses much active equipment, the floor, walls, and ceiling in an Equipment Room should be finished with a surface that is sealed to reduce dust. The finish should be of an anti-static nature and should not be dark in color as this will absorb and lower the overall lighting in the room.

Equipment Room Requirements 
  • The Equipment Room should be located where there is easy access to cabling pathways linking to either the horizontal cabling or to telecommunications rooms.
  • The minimum recommended size for this room is 14 m2.
  • The recommended practice is to provide 0.07 m2 of Equipment Room space for every 10 m2 of usable floor space (work areas).
  • The Equipment Room should be environmentally stable at 20 deg Celsius or 68 deg Fahrenheit.
  • Consideration should be given to the installation of an air conditioning unit in the Equipment Room in order maintain a stable temperature and minimize humidity levels.

Backbone Cabling 

Backbone Cabling provides inter-connection between telecommunications closets, equipment rooms and entrance facilities. It consists of the backbone cables, intermediate and main cross connects, mechanical terminations and patch cords or jumpers used for backbone-to-backbone cross-connection. This includes: vertical connection between floors (risers); cables between an equipment room and building cable entrance facilities; and cables between buildings (interbuilding).

Electromagnetic Interference (EMI) is an important factor during the design and installation of Backbone Cabling and pathways. Care should be taken to choose a Backbone Cabling System that suits the environment into which it will be installed.

Backbone Cabling Requirements 
  • The Backbone Cabling should use the conventional hierarchical star topology.
  • There should be no more than two hierarchical levels of cross-connects in the Backbone Cabling. This limitation of two levels of Cross-Connects is used in order to limit the degradation of signals and to simplify additions and changes.
  • The first level in the backbone topology is the cabling from the Main Cross-Connect.
  • The second level will be the cabling from the Intermediate Cross-Connect.

Telecommunications Rooms

A Telecommunications Room is the area within a building that houses the telecommunications cabling system equipment. This includes the mechanical terminations and/or cross-connect for the horizontal and backbone cabling system, such as patch panels and cabinets etc. 

It also houses active equipment such as switches and acts as a transition point between backbone and horizontal equipment.

Telecommunications Room Requirements 
  • The Telecommunications Room shall not be located in any area that can be affected by excessive heat, humidity or flooding.
  • The Telecommunications Room will be set up in such a way as to allow for housing of the telecommunications equipment.
  • EMI issues will be considered when setting up the Telecommunications Room.
  • Provide 0.07m2 of Telecommunications Room space for every 10m2 of work area space.
  • The Telecommunications Room shall be designed to a minimum of 14m2.
  • Cable management, cable routing, and cabling support (such as cable) shall be employed for effective management of all cables and connecting hardware in the Telecommunications Room.
  • The Telecommunications Room shall be dedicated to the telecommunications function. 
Telecommunications Room Recommendations
  • Should be located where there is easy access to cabling pathways linking to either the horizontal cabling or to the Telecommunications Room.
  • The Telecommunications Room size should be based on the floor space used.
  • The Telecommunications Room should be environmentally stable at 20 deg Celsius.
  • Access to the Telecommunications Room should be restricted to authorized service personnel and should not be shared with building services. 

Horizontal Cabling 

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 point or transition point connector, horizontal cable, and the mechanical terminations and patch cords (or jumpers) that comprises the horizontal cross-connect.

Points specified for the Horizontal Cabling Subsystem
  • Application specific components shall not be installed as the part of the Horizontal Cabling.
  • The proximity of Horizontal Cabling to sources of EMI shall be taken into account.
  • One transition point (TP) is allowed between different forms of the same cable type.
  • Additional outlets may be provided. These outlets are in addition to and may not replace the minimum requirements of the standard.
  • The Horizontal Cabling shall be configured in a star topology.
  • Bridged taps and splices are not allowed for copper-based Horizontal Cabling.
  • The length of cable between the Outlet/connector and the Horizontal Cross-connect shall not exceed 90 m (295 ft).
  • The total length of Horizontal Cross-connection, including the equipment cable, shall not exceed 5 m.
  • No section of conduit can be longer than 30 m (100 ft.).
  • No section of conduit can contain more than two 90° bends between pull points or pull boxes.

Work-Area Components 

The Work Area is defined as the connection between the Telecommunications Outlet and the station equipment (such as telephones, printers and video monitors). It consists of cords, adapters, and other transmission electronics, such as wireless access points, that permit the station equipment to connect to the horizontal media via the Telecommunications Outlet.

Work Area Components

  • Station Equipment computers, data terminals, telephones, etc
  • Patch Cables modular cords, PC adapter cables, fiber jumpers, etc
  • Adapters and media convert-ers such as those used for cabling transposition, adapter plugs/jacks, DB25, DB15, DB09 adapters, coaxial conversion (baluns) etc.
  • Adapters baluns etc. must be external to the Telecommun-ications Outlet used for equipment cords in the work area.
Work Area Cabling Requirements 
  • All devices that are specifically intended to support a given application shall be installed external to the Telecommunications Outlet/connector.
  • Horizontal cables shall be terminated on connecting hardware that meets the requirements specified in the Horizontal Distribution section of this manual.
  • All uninterrupted 4-pair balanced twisted-pair cables wired to the Telecommunications Outlet/connector shall have all 4-pairs terminated in an eight position, modular outlet at or near the Work Area.
  • When terminating to a Multi-user Telecommunications Outlet Assembly or Consolidation Point, all cable pairs shall be terminated.
  • Balanced twisted-pair pin/pair assignments - the T568A wiring scheme is preferred, however the T568B wiring scheme may be used if necessary to accommodate certain 8-pin cabling systems.
  • Telecommunications Outlet/connectors shall be securely mounted at planned locations.
  • When using pathways incorporated into furniture or partitions, pathways shall comply with all applicable codes and regulations.
  • Horizontal cable that runs between the Tele-communications Room and the Telecommun-ications Outlet/connector shall not be routed in the Work Area or other spaces with public access.

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