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Premise Wiring

| The Industry Standard | Backbone Wiring | Horizontal Wiring | Work Area Wiring | The Telecommunications Closet |
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Equipment Room Wiring | Cabling Administration | Media for Backbone Cabling | Media for Horizontal Cabling |
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Media for Work Area Cabling | Media for Telecommunications Closet Cabling | Media for Equipment Room Cabling |
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Types of Conductors | Shielding | Insulation & Jackets |

 

Some experts estimate that 70% of network failures are primarily caused by cable-related problems, so the cables are really important. Below you will find general information about premise wiring. Please call us or request a quote for any cabling project you have. We will be happy to help you find the best solution within your budget.

The TIA/EIA-568 Standard

Developed jointly by the Telecommunications  Industries Association and the Electronic Industries Association,  TIA/EIA-568 specifies complete electrical and physical guidelines  for industry-standard premise wiring systems. As specified by the TIA/EIA, a fully functional premise  wiring system is the result of multiple subsystems working  together as a single network.

Backbone Wiring encompasses all wiring between telecommunications  closets, equipment rooms, and entrance facilities, including  all cables, mechanical cable terminations, and intermediate  and main cross-connects. Backbone wiring runs between telecommunications  closets, equipment rooms and entrance facilities on the  same floor, from floor to floor, and even between buildings.

 

Horizontal Wiring encompasses all cable from a work-area wallplate or network connection  to the telecommunications closet. The outlets, cable,  and cross-connects in the closet are all part of the  horizontal wiring, which gets its name because the  cable typically runs horizontally above ceilings or  along the floor.

The work area includes all cable components between a horizontal-wiring wallplate or LAN outlet and  end-user telecomm devices, such as telephones, data terminals,  computers, modems, etc. Work-area components can include  connectors, cables, adapters, terminators, and more.

The telecommunications (or wiring) closet is a room or cabinet that holds distribution frames, cross-connects, and other hardware  needed to connect horizontal wiring to backbone wiring.  Each building must have at least one wiring closet.

An equipment room houses building telecommunications systems such as PBXs, servers, and the mechanical terminations of the telecomm wiring system. Considered different than a wiring closet because of the complexity of the components it contains, an equipment room nonetheless may take the place of a building's wiring closet or it may be a separate entity.

Unlike the other five components of premise wiring systems, cabling administration isn't a  place. It's a thing—a process that includes all  aspects of premise wiring related to documenting and managing  the system, testing the system, as well as the architectural  plans for the system.

Recommended media for backbone cabling

Unshielded twisted-pair (UTP) cable - Choose  4-pair, 100-ohm, solid-conductor UTP cable for short- to  medium-distance backbone cable in voice and data networks.  Solid-conductor cables are intended for stable runs and  shouldn't be subject to repeated flexing or twisting.  We recommend Category 5 or the newly ratified Category 5e  cable for new UTP installations to avoid expensive rewiring  in the future.

Shielded twisted-pair (STP) cable - Use  2-pair, 150-ohm shielded twisted-pair cable for IBM®  Token Ring networks. Type 1A STP cable is constructed of  four solid copper strands wrapped in a foil shield. Type  2A STP cable includes an extra 4-pair UTP strand for phone  circuits.

Fiber optic cable - Even though  fiber is more expensive and requires more careful handing  than other cables, it's the preferred medium for backbone  cable because it offers maximum range, bandwidth, and flexibility. Compact and lightweight, fiber provides high-speed transmission  over a wide bandwidth. Fiber also carries data over much  farther distances than copper cable, and it's immune  to EMI (electromagnetic interference). Fiber backbone cable is also far less likely to require replacement.

Coaxial cable - Although recognized by the TIA/EIA as a suitable, economical choice for backbone cable in small, Thin Ethernet (10BASE2) applications, our technical experts don't recommend 50-ohm coaxial cable for new installations.

Recommended media for horizontal cabling

UTP - Low cost, 100-ohm UTP cable  supports a range of applications up to 100 MHz, making it  a preferred medium for horizontal wiring. If you plan to install UTP, you must decide which type  (or category) of cable you'll need. Although Category  3 or 4 cable is sufficient for most data and voice systems,  Category 5 and Enhanced Category 5 (CAT5e) are highly recommended  because they're certified to support any application  operating up to 100 MHz or higher.
CAT5e is an excellent choice for high-speed networks. If  future upgrades will require faster speeds, then installing  CAT5e cable now could prevent the need for recabling in  the future.

STP - This 150-ohm twisted-pair wire is usually  installed as a hybrid system. Called Type 2A, hybrid cable  consists of one 150-ohm STP data cable and one 100-ohm UTP  Category 3 voice cable, both in the same sheath. This type  of cable is generally used for Token Ring applications.  But thanks to its extended bandwidth, STP can also be used  for broadband video applications up to 300 MHz or for 155-Mbps  ATM. TIA/EIA TSB-53 defines STP's extended specifications.

Fiber optic - Because of its increased bandwidth  capabilities and the availability of work-area outlet connectibility,  fiber optic cable is becoming a popular choice for horizontal  connections. The TIA/EIA-568A standard recognizes two fiber  types: 9/125 µm for single-mode applications and 62.5/125  µm for multimode applications. Optical signal wavelengths of 1310/1550 nm for single-mode  fiber and 850/1300 nm for multimode fiber are commonly used  to transmit data. For testing, an 850-nm signal is recommended  for multimode; 1300-nm for single-mode.

Coaxial cable - As with backbone cable, coax  isn't recommended for horizontal wiring, because the  entire system could collapse if one cable is disrupted.

The work area outlet

The work area encompasses all cabling from wall outlets  to end-user devices such as terminals, workstations, telephones,  etc. It includes the wallplate itself, connectors, even  the adapters that link cabling to the wall outlet. Work  areas are designed to tolerate frequent moves, but they  still need careful management. T568-A is generally used for analog voice applications  requiring two lines. T568-B is more commonly used for data  applications. Take care to ensure that all terminating hardware  has the same Category and pinning specification as your  cable, because mixing the two standards may result in crossed  pairs that can bring down your network. Also be careful to follow standard procedures when installing  work area outlets. For example, because of patch-cord length  limits, power cables and outlet locations must be properly  separated. Ensure the proper amount of twists in each cable,  observe bend-radius limits, be careful not to bundle cables  too tightly, etc.

The telecommunications closet

This is the service point housing all equipment associated  with telecomm wiring systems. Its primary function is to  serve as a termination point for the horizontal cabling  system, but all transmission media terminates in this area. The closet houses cross-connects and all associated electronic equipment, backbone and horizontal cabling, and associated  pathways for the cable. Most auxiliary equipment is also  usually housed in this area, including security systems,  key-entry systems, file servers, etc. Depending on the size of the service area, the TIA/EIA-569  standard recommends at least one telecommunications closet  per floor. Specific closet sizes are also recommended, based  on service-area size. This ensures sufficient space for  all connecting hardware, as well as enough room for service  personnel to function without causing undue system disruptions. Adequate climate controls, lighting, and power supplies  are also specified. Figure 2 below shows the sample layout  of a typical telecommunications closet.

The equipment room

The equipment room houses all the telecommunications systems  and mechanical terminations of a premise-wiring system.  It's considered separate from the telecommunications  closet based on the complexity of the equipment it houses  (such as PBXs, computing equipment, switches, etc.); however,  all functions of an equipment room may be incorporated in  a wiring closet.

Types of Conductors

Copper cables have two types of conductors: solid or stranded.  Solid-conductor cables are less expensive, have better conductivity,  and are easier to terminate than stranded cables.

Additionally, solid-conductor cable is ideal for both backbone  and horizontal wiring. Despite these advantages, however,  solid-copper cable is comparatively inflexible, and breakage is likely if it's repeatedly bent or twisted. That's  why most twisted-pair cables today are made with stranded  conductors—smaller-gauge wires twisted together to  form a single conductor.

Stranded cable has two main advantages over solid-conductor cable: flexibility and durability. It's flexible enough  to bend back and forth, so it's much easier to work  with, and it's far more resistant to damage from minor  scratches or nicks that may occur during cable stripping. Because the conductor wires are twisted, very little surface  area is exposed to damage. In comparison, one small scratch  or nick on a solid-conductor cable may be enough to ruin  it, because far greater surface area is exposed to damage  from cutting or crushing forces.

Shielding

Twisted-pair cable shields are metallic covers (usually  copper or aluminum) that surround insulated conductors.  They're constructed of foil, wire strands, or braided  metal. Our techs recommend using shielded cable to protect  data transmissions from external EMI, which can cause signal  distortion or interference. The quality of a shield depends on its surface- transfer  impedance (STI), which indicates its ability to reduce EMI—especially  at high frequencies. The greater the reduction factor and  the less external voltage that's picked up inside the  cable, the better the shield. There are several types of  cable shields.

Solid metal tubes provide proper shielding  at all frequencies, which makes them the best of all. Unfortunately,  their rigid construction severely limits cable flexibility,  so they're used only in very special applications—industrial  environments where EMI, chemicals, and cable crushing pose  frequent threats.
Braided shields are made from very thin  40-32 AWG copper wire. The wire is woven into a braid with  one flat ribbon of wires winding clockwise around the cable  core and a second ribbon running counterclockwise. The result  is a stronger, more flexible cable. This type of shield  best defends against lower-frequency interference (less  than 10 MHz), such as that generated by AC electricity,  AM radio signals, and CB radios.

Note that a shield with a single braid can't provide  100% protection because of gaps in the weave, expecially  since these gaps may expand the conductors, leaving them  bent and flexed. Braided-shield cables offer 75-85% coverage and provide  adequate protection for most lower-frequency applications.  Cables subject to higher-frequency interference require  85-95% shielding, which can be achieved using double-braided  shields that offer up to 99% protection. Other types of shielding include spiral wire shields, foil  shields, and hybrid shields, all of which provide varying  degrees of shielding for different kinds of applications.

Insulation and Jackets

Cable insulation serves three purposes. First, it prevents  contact (or short circuits) between conductors. Second,  it prevents contact between conductors and the external  environment. Third, it controls heat dissipation.

Insulation in most cable consists of one or more types of plastics, which have a high resistance to the flow of electric current.

A cable jacket is the outer covering that surrounds a cable's  core, shields, and insulation. Its purpose is to protect  these components from mechanical damage, chemicals, moisture,  and exposure to harmful environmental conditions. Most jackets are made of extrudable plastics that are heated  and forced through a die to form a continuous coating around  the cable. Such jackets are rated for use according to the  ambient temperature of the environment in which they'll  be installed. For example, cables designed for use in plenums—a  building's air ducts—have jackets specially designed  to tolerate high temperatures.

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