Cable System and Infrastructure Constraints

Where Do Codes Come From?

Building, construction, and communications codes originate from a number of sources. Usually, these codes originate nationally rather than at the local, city, or county level. Local municipalities usually adopt these national codes as local laws. Other national codes are issued that affect the construction of electrical and communications equipment.

Two of the predominant national code governing bodies in the United States are the Federal Communications Commission (FCC) and the National Fire Protection Association (NFPA). The Americans with Disabilities Act (ADA) also affects the construction of cabling and communications facilities because it requires that facilities be constructed to provide universal access.

The Federal Communications Commission

The United States Federal Communications Commission (FCC) issues guidelines that govern the installation of telecommunications cabling and the design of communications devices built or used in the United States. The guidelines help prevent problems relating to communications equipment, including interference with the operation of other communications equipment. Part 68 of the FCC rules provides regulations that specifically address connecting premises cabling and customer-provided equipment to the regulated networks.

The FCC also publishes numerous reports and orders that deal with specific issues regarding communications cabling, electromagnetic emissions, and frequency bandwidths. The following is a list of some of the important documents issued by the FCC:

Part 68 of the FCC rules Governs the connection of premises equipment and wiring to the national network.

Telecommunications Act of 1996 Establishes new rules for provisioning and additional competition in telecommunications services.

CC Docket No. 81-216 Establishes rules for providing customer-owned premises wiring.

CC Docket No. 85-229 Includes the Computer Inquiry III review of the regulatory framework for competition in telecommunications.

Part 15 of the FCC rules Addresses electromagnetic radiation of equipment and cables.

CC Docket No. 87-124 Addresses implementing the ADA.

CC Docket No. 88-57 Defines the location of the demarcation point on a customer premise.

Fact Sheet ICB-FC-011 Deals with connection of one- and two-line terminal equipment to the telephone network and the installation of premises wiring.

Memorandum Opinion and Order FCC 85-343 Covers the rights of users to access embedded complex wire on customer premises.

Tip

Most of the FCC rules, orders, and reports can be viewed on the FCC website at www.fcc.gov. Since rules can change over time, it's wise to monitor updates.

The National Fire Protection Association

In 1897, a group of industry professionals (insurance, electrical, architectural, and other allied interests) formed the National Association of Fire Engineers with the purpose of writing and publishing the first guidelines for the safe installation of electrical systems and providing guidance to protect people, property, and the environment from fire. The guidelines are called the National Electrical Code (NEC). Until 1911, the group continued to meet and update the NEC. The National Fire Protection Association (NFPA), an international, nonprofit, membership organization representing over 65,000 members and 100 countries, now sponsors the NEC. The NFPA continues to publish the NEC as well as other recommendations for a variety of safety concerns.

The NEC is updated by various committees and code-making panels, each responsible for specific articles in the code.

Tip

You can find information about NFPA and many of its codes and standards at www.nfpa.org. You can purchase NFPA codes through Global Engineering Documents (http://global.ihs.com); major codes, such as the National Electrical Code, can be purchased at most bookstores.

The NEC is called NFPA 70 by the National Fire Protection Association, which also sponsors more than 600 other fire codes and standards that are used in the United States and throughout the world. The following are some examples of these documents:

NFPA 1 (Fire Prevention Code) Addresses basic fire-prevention requirements to protect buildings from hazards created by fire and explosion.

NFPA 13 (Installation of Sprinkler Systems) Addresses proper design and installation of sprinkler systems for all types of fires.

NFPA 54 (National Fuel Gas Code) Provides safety requirements for fuel-gas equipment installations, piping, and venting.

NFPA 70 (National Electrical Code) Deals with proper installation of electrical systems and equipment.

NFPA 70B (Recommended Practice for Electrical Equipment Maintenance) Provides guidelines for maintenance and inspection of electrical equipment such as batteries.

NFPA 70E (Standard for Electrical Safety in the Workplace) A basis for evaluating and providing electrical safety–related installation requirements, maintenance requirements, requirements for special equipment, and work practices. This document is compatible with OSHA (Occupational Safety and Health Administration) requirements.

NFPA 72 (National Fire Alarm Code) Provides a guide to the design, installation, testing, use, and maintenance of fire-alarm systems.

NFPA 75 (Standard for the Protection of Information Technology Equipment) Establishes requirements for computer room installations that require fire protection.

NFPA 101 (Life Safety Code) Deals with minimum building design, construction, operation, and maintenance requirements needed to protect building occupants from fire.

NFPA 262 (Standard Method of Test for Flame Travel and Smoke of Wires and Cables for Use in Air-Handling Spaces) Describes techniques for testing visible smoke and fire-spreading characteristics of wires and cables.

NFPA 780 (Standard for the Installation of Lightning Protection Systems) Establishes guidelines for protection of buildings, people, and special structures from lightning strikes.

NFPA 1221 (Standard for the Installation, Maintenance, and Use of Emergency Services Communications System) Provides guidance for fire service communications systems used for emergency notification. This guide incorporates NFPA 297 (Guide on Principles and Practices for Communications Systems).

These codes are updated every few years; the NEC, for example, is updated every three years. It was updated in 2008 and will be updated again in 2011.

You can purchase guides to the NEC that make the code easier for the layperson to understand. Like the NEC, these guides may be purchased at almost any technical or large bookstore. You can also purchase the NEC online from the NFPA's excellent website at www.nfpa.org.

If you are responsible for the design of a telecommunications infrastructure, a solid understanding of the NEC is essential. Otherwise, your installation may run into all sorts of red tape from your local municipality.

Underwriters Laboratories

Underwriters Laboratories, Inc. (UL) is a nonprofit product safety testing and certification organization. Once an electrical product has been tested, UL allows the manufacturer to place the UL listing mark on the product or product packaging.

KEY TERM: UL listed or UL recognized

The UL mark identifies whether a product is UL listed or UL recognized. If a product carries the UL Listing Mark (UL in a circle) followed by the word LISTED, an alphanumeric control number, and the product name, it means that the complete (all components) product has been tested against the UL's nationally recognized safety standards and found to be reasonably free of electrical shock risk, fire risk, and other related hazards. If a product carries the UL Recognized Component Mark (the symbol looks like a backward R and J), it means that individual components may have been tested but not the complete product. This mark may also indicate that testing or evaluation of all the components is incomplete.

You may find a number of different UL marks on a product listed by the UL (all UL listing marks contain UL inside a circle). Some of these include:

UL The most common of the UL marks, this mark indicates that samples of the complete product have met UL's safety requirements.

C-UL This UL mark is applied to products that have been tested (by Underwriters Laboratories) according to Canadian safety requirements and can be sold in the Canadian market.

C-UL-US This is a relatively new listing mark that indicates compliance with both Canadian and U.S. requirements.

UL-Classified This mark indicates that the product has been evaluated for a limited range of hazards or is suitable for use under limited or special conditions. Specialized equipment such as firefighting gear, industrial trucks, and other industrial equipment carry this mark.

C-UL-Classified This is the classification marking for products that the UL has evaluated for specific hazards or properties, according to Canadian standards.

C-UL-Classified-US Products with this classification marking meet the classified compliance standards for both the United States and Canada.

Recognized Component Mark (backward R and J) Products with the backward R and J have been evaluated by the UL but are designed to be part of a larger system. Examples are the power supply, circuit board, disk drives, CD-ROM drive, and other components of a computer. The Canadian designator (a C preceding the Recognized Component Mark) is the Canadian equivalent.

C-Recognized Component-US The marking indicates a component certified by the UL according to both the U.S. and Canadian requirements.

International EMC mark The electromagnetic compatibility mark indicates that the product meets the electromagnetic requirements for Europe, the United States, Japan, and Australia (or any combination of the four). In the United States, this mark is required for some products, including radios, microwaves, medical equipment, and radio-controlled equipment.

Other marks on equipment include the Food Service Product Certification mark, the Field Evaluated Product mark, the Facility Registration mark, and the Marine UL mark.

Tip

To see examples of the UL marks we've described, visit www.ul.com.

The NEC requires that Nationally Recognized Test Laboratories (NRTL) rate communications cables used in commercial and residential products as "listed for the purpose." Usually UL is used to provide listing services, but the NEC only requires that the listing be done by an NRTL; other laboratories, therefore, can provide the same services. One such alternate testing laboratory is Intertek ETL SEMKO (www.usa.intertek-etlsemko.com).

More than 750 UL standards and standard safety tests exist; some of the ones used for evaluating cabling-related products are:

UL 444 Applies to testing multiple conductors, jacketed cables, single or multiple coaxial cables, and optical fiber cables. This test applies to communications cables intended to be used in accordance with the NEC Article 800 or the Canadian Electrical Code (Part I) Section 60.

NFPA 262 (formerly UL 910) Applies to testing the flame spread and smoke density (visible smoke) for electrical and optical fiber cables used in spaces that handle environmental air (that's a fancy way to say the plenum). This test does not investigate the level of toxic or corrosive elements in the smoke produced, nor does it cover cable construction or electrical performance. NEC Article 800 specifies that cables that have passed this test can carry the NEC flame rating designation CMP (communications multipurpose plenum).

UL 1581 Applies to testing flame-spread properties of a cable designed for general-purpose or limited use. This standard contains details of the conductors, insulation, jackets, and coverings, as well as the methods for testing preparation. The measurement and calculation specifications given in UL 1581 are used in UL 44 (Standards for the Thermoset-Insulated Wires and Cables), UL 83 (Thermoplastic-Insulated Wires and Cables), UL 62 (the Standard for Safety of Flexible Cord), and UL 854 (Service-Entrance Cables). NEC Article 800 specifies that cables that have passed these tests can carry the NEC flame-rating designation CMG, CM, or CMX (all of which mean communications general-purpose cable).

UL 1666 Applies to testing flame-propagation height for electrical and optical fiber cables installed in vertical shafts (the riser). This test only makes sure that flames will not spread from one floor to another. It does not test for visible smoke, toxicity, or corrosiveness of the products' combustion. It does not evaluate the construction for any cable or the cable's electrical performance. NEC Article 800 specifies that cables that have passed this test may carry a designation of CMR (communications riser).

UL has an excellent website that has summaries of all the UL standards and provides access to its newsletters. The main UL website is www.ul.com; a separate website for the UL Standards Department is located at http://ulstandardsinfonet.ul.com. UL standards may be purchased through IHS/Global at http://global.ihs.com.

Codes and the Law

At the state level in the United States, many public utility/service commissions issue their own rules governing the installation of cabling and equipment in public buildings. States also monitor tariffs on the state's service providers.

At the local level, the state, county, city, or other authoritative jurisdiction issues codes. Most local governments issue their own codes that must be adhered to when installing communications cabling or devices in the jurisdictions under their authority. Usually, the NEC is the basis for electrical codes, but often the local code will be stricter.

Over whom the jurisdiction has authority must be determined prior to any work being initiated. Most localities have a code office, a fire marshal, or a permitting office that must be consulted.

The strictness of the local codes will vary from location to location and often reflects a particular geographic region's potential for or experience with a disaster. For example:

• Some localities in California have strict earthquake codes regarding how equipment and racks must be attached to buildings.
• In Chicago, some localities require that all cables be installed in metal conduits so that cables will not catch fire easily. This is also to help prevent flame spread that some cables may cause.
• Las Vegas has strict fire-containment codes that require firestopping of openings between floors and firewalls. These openings may be used for running horizontal or backbone cabling.

Warning

Local codes take precedence over all other installation guidelines. Ignorance of local codes could result in fines, having to reinstall all components, or the inability to obtain a Certificate of Occupancy.

Localities may adopt any version of the NEC or write their own codes. Don't assume that a specific city, county, or state has adopted the NEC word for word. Contact the local building codes, construction, or building permits department to be sure that what you are doing is legal.

Historically, telecommunications cable installations were not subject to local codes or inspections. However, during several commercial building fires, the communications cables burned and produced toxic smoke and fumes, and the smoke obscured the building's exit points. This contributed to deaths. When the smoke mixed with the water vapor, hydrochloric acid was produced, resulting in significant property damage. Because of these fires, most JHAs now issue permits and perform inspections of the communications cabling.

It is impossible to completely eliminate toxic elements in smoke. Corrosive elements, although certainly harmful to people, are more a hazard to electronic equipment and other building facilities. The NEC flame ratings for communications cables are designed to limit the spread of the fire and, in the case of plenum cables, the production of visible smoke that could obscure exits. The strategy is to allow sufficient time for people to exit the building and to minimize potential property damage. By specifying acceptable limits of toxic or corrosive elements in the smoke and fumes, NFPA is not trying to make the burning cables "safe." Note, however, that there are exceptions to the previous statement, notably cables used in transportation tunnels, where egress points are limited.

Tip

If a municipal building inspector inspects your cabling installation and denies you a permit (such as a Certificate of Occupancy), he or she must tell you exactly which codes you are not in compliance with.

UTP, Optical Fiber, and Future-Proofing

The common networking technologies today (Ethernet, Token Ring, FDDI, and ATM) can all use either UTP or optical fiber cabling, and IT professionals are faced with the choice. MIS managers and network administrators hear much about "future-proofing" their cabling infrastructures. The claim is that installing particular grades of cable and components will guarantee that you won't have to ever update your cabling system again. However, you should keep in mind that in the early 1990s network managers thought they were future-proofing their cabling system when they installed Category 4 rather than Category 3 cabling.

Today, decision makers who must choose between Category 6 and 6A cabling components are thinking about future-proofing. Each category is an improvement in potential data throughput and therefore a measure of future-proofing. Deciding whether to use optical fiber adds to the decision. Here are some of the advantages of using optical fiber:

• It has much higher potential bandwidth, which means that the data throughput is much greater than with copper cable. Optical fiber cable has the potential for higher bandwidth, because it requires a transceiver to deliver the bandwidth. If the highest bandwidth optical transceiver currently available is 10GB, then its actual bandwidth is no better 10GBase-T, notwithstanding the distance capability.
• It's not susceptible to electromagnetic interference.
• It can transmit over longer distances, which is useful for centralized cabling topologies and backbone cabling, although distance is set at 100 meters for the run of cable from the TR to equipment outlets regardless of media, according to ANSI/TIA-568-C.
• Optical fiber also allows the use of telecommunications enclosures, since it can support longer backbone distances than UTP. This essentially places the switches closer to the equipment outlets and can provide savings of approximately 25 percent over the use of switches in TRs. (For more information, see the TIA Fiber Optics LAN Section at www.fols.org)
• Improved termination techniques and equipment make it easier to install and test.
• Cable, connectors, and patch panels are now cheaper than before.
• It's valuable in situations where EMI is especially high.
• It offers better security (because the cable cannot be easily tapped or monitored).

UTP cabling is still popular in a traditional hierarchical topology where an intermediate switch is used in a TR, and you may want to consider remaining with UTP cabling for the following reasons:

• The TIA estimates that the combined installation and hardware costs result in a finished centralized cabling fiber optic network that is 30 percent more expensive than a Category 5e or 6 copper cable network using a traditional hierarchical star topology. However, these cost differences are expected to decrease with time.
• If higher bandwidth (more than a gigabit per second) requirements are not an issue for you, you may not need optical fiber.
• Fiber optics is the medium of choice for security only if security concerns are unusually critical.
• EMI interference is only an issue if it is extreme.

Fiber-optic cabling and transmission media are likely to outpace copper for 100 meter links as speeds increase; however, when considering optical fiber cable, remember that you are trying to guarantee that the cabling system will not have to be replaced for a very long time, regardless of future networking technologies. Some questions you should ask yourself when deciding if fiber optic is right for you include the following:

• Do you rent or own your current location?
• If you rent, how long is your lease, and will you be renewing your lease when it is up?
• Are there major renovations planned that would cause walls to be torn out and rebuilt?

As network applications are evolving, better UTP and optical fiber cabling media are required to keep up with bandwidth demand. As you will see from standards, the end user has many options in a media category. There are many types of UTP and optical fiber cabling. Standards will continue to evolve, but it's always a good idea to install the best grade of cabling since the cost of the structured cabling systems (excluding installation cost) is usually only 5–10 percent of the total project cost. Therefore, making the right decisions today can greatly future-proof the network.

Topologies | Choosing the Correct Cabling

The network's topology refers to the physical layout of the elements of the telecommunications cabling system structure (e.g., main equipment room, cross-connections, telecommunications rooms and enclosures, switches, and hubs) that make up the network. Choosing the right topology is important because the topology affects the type of networking equipment, cabling, growth path, and network management.

Today's networking architectures fall into one of three categories:

• Hierarchical star
• Bus
• Ring

Topologies are tricky because some networking architectures appear to be one type of technology but are in reality another. Token Ring is a good example of this because Token Ring uses hubs (multistation access units or MAUs). All stations are connected to a central hub, so physically it is a hierarchical star topology; logically, though, it is a ring topology. Often two topology types will be used together to expand a network.

Physical vs. Virtual Topology

Topology refers to the physical layout of the wiring and key connection points of a network, and it also refers to the network's method of transmitting data and to the logical, orvirtual, layout of its connection points. Before the advent of structured wiring, physical and logical topology were often the same. For example, a network that had a ring topology actually had the wiring running from point to point in a ring. This can be confusing these days. The implementation of structured wiring standardized a hierarchical star configuration as the physical topology for modern networks, and network electronics take care of the logical topologies.

Hierarchical Star Topology

When implementing a hierarchical star topology, all computers are connected to a single, centrally located point. This central point is usually a hub of servers and switches located in the main equipment room and interconnected through the main cross-connection. All cabling used in a hierarchical star topology is run from the equipment outlets back to this central location. Typically in commercial buildings, there is a horizontal cross-connection with a workgroup switch located in a telecommunications room (TR) that allows backbone cabling to interconnect with horizontal cabling. Usually, the utilization of switch ports is low. In other words, only 70–80 percent of the ports in a switch are connected. Essentially, you are paying for more ports than you are using.

A lower-cost method involves placing horizontal cross-connections and workgroup switches in telecommunications enclosures. This is standardized in ANSI/TIA-568-C and is commonly referred to as fiber-to-the-telecommunications enclosure (FTTE). These house mini-patch panels and switches and are located in enclosures, installed overhead or on wall space, very close to clusters of equipment outlets. One benefit of this implementation of the hierarchical star is that the utilization of switch ports is typically 90 percent or greater. Another benefit is that TRs can be smaller, reducing power and HVAC requirements since TRs do not house the equipment and patch panels. Studies performed by TIA's Fiber Optic LAN Section have shown that the reduction of TR space and utility requirements, combined with lower costs in switches and ports, can lead to savings of 25 percent or more compared to a traditional implementation of hierarchical star where switches are located in TRs. One practical disadvantage of FTTE that has been raised by some users is the need to service equipment out in the work space environment (for example, above office cubes) as opposed to in a TR.

Another alternative implementation of a hierarchical star topology per ANSI/TIA-568-C is called centralized cabling. Centralized cabling is a hierarchical star topology that extends from the main cross-connection in an equipment room directly to an equipment outlet by allowing a cable to be pulled through a telecommunications room (or enclosure) without passing through a switch. The cable can be a continuous sheath of cable from the equipment room, or two separate cables may be spliced or interconnected in the TR. In either case, there is no need to use a workgroup switch in a TR to interconnect a backbone cable to a horizontal cable since all electronics are centralized in the main equipment room. This subset of the hierarchical star topology is commonly referred to as fiber-to-the-desk (FTTD) since it employs fiber to support the greater than 100 meter distances from the main equipment room/cross-connection to the equipment/telecommunications outlet. However, media converters or optical NICs are required to convert from optical to electrical near the equipment outlets. The centralized cabling topology can produce savings by reducing the size of TRs and need for HVAC since no active equipment is used in the TR. TIA's Fiber Optic LAN Section (www.fols.org) has studied this topology in detail and provides good information on its benefits.

 Hierarchical star topology with a central hub to support FTTD

Cabling @ Work: High School Decides to Use Optical Fiber Cabling

A new school recently designed a new communications network. They decided to use an optical fiber network. Why? Let's take a look.

Why ABC High Uses Optical Fiber Cabling

ABC High chose to use optical fiber cabling for two primary reasons:

Link lengths By taking advantage of the long data runs supported by multimode fiber, network planners were able to consolidate electronics into a single, centrally located wiring closet. This approach drastically reduced the amount of electronics needed for the installation and lowered the cost of (and simplified) network maintenance.

Network longevity School administrators realized that additional "headroom" would become essential in future programs and/or applications. This cabling system provides a quick and easy way to upgrade the system in years to come.

Installation Details

The new high school has 32 classrooms and accommodates approximately 650 students in grades 9–12. School administrators chose a centralized cabling network topology with a switch serving as the backbone.

Within the building, a single, centrally located wiring closet forms the heart of the network cabling plant, with OM3 50/125 micron (per ISO 11801 Ed. 2) multimode fiber links radiating to each of the classrooms and other areas throughout the building. There are at least seven network drops in each classroom.

The use of small form-factor connectors is valuable as it allows large numbers of fibers to be terminated in a small panel space.

From the perspective of cabling, the hierarchical star topology is now almost universal. It is also the easiest of the three networking architectures to cable. The ANSI/TIA-568-C and ISO/IEC 11801 Ed. 2 standards assume that the network architecture uses a hierarchical star topology as its physical configuration. If a single node on the star fails or the cable to that node fails, then only that single node fails. However, if the hub fails, then the entire star fails. Regardless, identifying and troubleshooting the failed component is much easier than with other configurations because every node can be isolated and checked from the central distribution point. In this topology, the network speed capability of the backbone is typically designed to be 10 times that of the horizontal system. For example, if the equipment outlets and desktops are provisioned to run 100Mbps in the horizontal, then these links are usually connected to a workgroup switch that has a 1Gbps uplink connected to the building riser backbone cable. If the horizontal links were designed to operate at 1Gbps, then the backbone should be capable of operating at 10Gbps if it is expected that the aggregate load of the horizontal connections on the switch will be close to 10Gbps. Although you may not need to implement the hardware to support these speeds on day one, it is smart to design the cabling media with a 10:1 ratio to support future bandwidth growth.

From this point on in the chapter, we will assume you understand that the physical layout of a modern network is a hierarchical star topology and that when we discuss bus and ring topologies we're referring to the logical layout of the network.

Killing an Entire Hierarchical Star Topology

Although a single node failure cannot usually take down an entire star topology, sometimes it can. In some circumstances, a node fails and causes interference for the entire star. In other cases, shorts in a single cable can send disruptive electrical signals back to the hub and cause the entire star to cease functioning. Of course, failure of the hub will also affect all nodes in a star topology. (Just as you need diversity and redundancy in cabling/network paths, you need diversity and redundancy in your switches as well.)

Bus Topology

The bus topology is the simplest network topology. Also known as a linear bus, in this topology all computers are connected to a contiguous cable or a cable joined together to make it contiguous. 

 Bus topology

Ethernet is a common example of a bus topology. Each computer determines when the network is not busy and transmits data as needed. Computers in a bus topology listen only for transmissions from other computers; they do not repeat or forward the transmission on to other computers.

The signal in a bus topology travels to both ends of the cable. To keep the signal from bouncing back and forth along the cable, both ends of the cable in a bus topology must be terminated. A component called a terminator, essentially nothing more than a resistor, is placed on both ends of the copper (coax) cable. The terminator absorbs the signal and keeps it from ringing, which is also known as overshoot or resonance; this is referred to as maximum impedance. If either terminator is removed or if the cable is cut anywhere along its length, all computers on the bus will fail to communicate.

Coaxial cabling was most commonly used in true bus-topology networks such as thin/thick Ethernet. However, UTP-based cabling Ethernet applications like 10Base-T, 100Base-T, and above still function as if they were a bus topology even though they are wired as a hierarchical star topology.

Ring Topology

A ring topology requires that all computers be connected in a contiguous circle. The ring has no ends or hub. Each computer in the ring receives signals (data) from its neighbor, repeats the signal, and passes it along to the next node in the ring. Because the signal has to pass through each computer on the ring, a single node or cable failure can take the entire ring down.

Ring topology

A true ring topology is a pain in the neck to install cable for because the circular nature of the ring makes it difficult to expand a ring over a large physical area. Token Ring is a ring topology. Even though Token Ring stations may be connected to a central MAU (and thus appear to be a star topology), the data on the Token Ring travels from one node to another. It passes through the MAU each time.

ISO/IEC 11801

ISO/IEC 11801

The International Organization for Standardization (ISO) and the International Electrotechnical Commission (IEC) publish the ISO/IEC 11801 standard predominantly used in Europe. This standard was released in 1995 and is similar in many ways to the ANSI/TIA-568-C standard upon which it is based. The second edition was released in 2002 and is largely in harmony with ANSI/TIA-568-C. However, the ISO/IEC 11801 standard has a number of differences in terminology. Table 1 shows the common codes and elements of an ISO/IEC 11801 structured cabling system.

Differences between ANSI/TIA-568-C and ISO/IEC 11801

Differences between ANSI/TIA-568-C and ISO/IEC 11801 Ed. 2 include the following:

• ISO/IEC 11801 allows for an additional media type for use with backbone and horizontal cabling and 120 ohm UTP.
• The term consolidation point is much broader in ISO/IEC 11801; it includes not only transition points for under-carpet cable to round cable (as defined by ANSI/TIA-568-C), but also consolidation point connections.

Table 1: Common Codes and Elements Defined by ISO/IEC 11801 

Element	Code	Description
Building distributor	BD	A distributor in which building-to-building backbone cabling terminates and where connections to interbuilding or campus backbone cables are made.
Building entrance facilities	BEF	Location provided for the electrical and mechanical services necessary to support telecommunications cabling entering a building.
Campus distributor	CD	Distributor location from which campus backbone cabling emanates.
Equipment room	ER	Location within a building dedicated to housing distributors and application-specific equipment.
Floor distributor	FD	A distributor used to connect horizontal cable to other cabling subsystems or equipment.
Horizontal cable	HC	Cable from the floor distributor to the telecommunications outlet.
Telecommunications room	TC	Cross-connection point between backbone cabling and horizontal cabling. May house telecommunications equipment, cable terminations, cross-connect cabling, and data networking equipment.
Telecommunications outlet	TO	The point where the horizontal cabling terminates on a wall plate or other permanent fixture. The point is an interface to the work area cabling.
Consolidation point	CP	The location in horizontal cabling where a cable may end, which is not subject to moves and changes, and another cable starts leading to a telecommunications outlet, which easily adapts to changes.
Work-area cable	None	Connects equipment in the work area (phones, computers, etc.) to the telecommunications outlet.

ISO/IEC 11801 Ed. 2 specifies a maximum permanent link length of 90 meters and a maximum channel link of 100 meters. Patch and equipment cord maximum lengths may be adjusted by formulas depending on the actual link lengths. Terminology differences between ANSI/TIA-568-C and ISO/IEC 11801 Ed. 2 include the following:

• The ISO/IEC 11801 Ed. 2 definition of the campus distributor (CD) is similar to the ANSI/TIA-568-C definition of a main cross-connect (MC).
• The ISO/IEC 11801 Ed. 2 definition of a building distributor (BD) is equal to the ANSI/TIA-568-C definition of an intermediate cross-connect (IC).
• The ISO/IEC 11801 Ed. 2 definition of a floor distributor (FD) is defined by ANSI/TIA-568-C as the horizontal cross-connect (HC).

Classification of Applications and Links

ISO/IEC 11801 Ed. 2 defines classes of applications and links based on the type of media used and the frequency requirements. ISO/IEC 11801 Ed. 2 specifies the following classes or channels of applications and links:

Class A For voice and low-frequency applications up to 100kHz.

Class B For low-speed data applications operating at frequencies up to 1MHz.

Class C For medium-speed data applications operating at frequencies up to 16MHz.

Class D Concerns high-speed applications operating at frequencies up to 100MHz.

Class E Concerns high-speed applications operating at frequencies up to 250MHz.

Class E_A Concerns high-speed applications operating at frequencies up to 500MHz.

Class F Concerns high-speed applications operating at frequencies up to 600MHz.

Class F_A Concerns high-speed applications operating at frequencies up to 1000MHz.

Optical Class An optional class for applications where bandwidth is not a limiting factor.

ANSI/TIA-570-B

ANSI and TIA published ANSI/TIA-570-B-2004, or the Residential and Light Commercial Telecommunications Cabling Standard, to address the growing need for "data-ready" homes and multidwelling residential buildings. Just a few years ago, only the most serious geeks would have admitted to having a network in their homes. Today, more and more homes have small networks consisting of two or more home computers, a cable modem, and a shared printer. Even apartment buildings and condominiums are being built or remodeled to include data outlets; some apartment buildings and condos even provide direct Internet access.

Cabling @Work: An Example of Poor Grounding

One of the best examples we can think of that illustrates poor grounding practices was a very large building that accidentally had two main grounds installed, one on each side. (A building should only have one main ground.) A telecommunications backbone cable was then grounded to each main ground.

Under some circumstances, a ground loop formed that caused this cable to emit EMI at specific frequencies. This frequency just so happened to be used by air traffic control beacons. When the building cable emitted signals on this frequency, it caused pilots to think they were closer to the airport than they really were. One plane almost crashed as a result of this poorly grounded building. The FAA (Federal Aviation Administration) and the FCC (Federal Communications Commission) closed the building and shut down all electrical systems for weeks until the problem was eventually found.

The ANSI/TIA-570-B standard provides requirements for residential telecommunications cabling for two grades of information outlets: basic and multimedia cabling. This cabling is intended to support applications such as voice, data, video, home automation, alarm systems, environmental controls, and intercoms. The two grades are as follows:

Grade 1 This grade supports basic telephone and video services. The standard specifies twisted-pair cable and coaxial cable placed in a star topology. Grade 1 cabling requirements consist of a minimum of one four-pair UTP cable that meets or exceeds the requirements for Category 5e, a minimum of one 75-ohm coaxial cable, and their respective connectors at each telecommunications outlet and the DD. Installation of Category 6 cable in place of Category 5e cable is recommended.

Grade 2 Grade 2 provides a generic cabling system that meets the minimum requirements for basic and advanced telecommunications services such as high-speed Internet and in-home generated video. Grade 2 specifies twisted-pair cable, coaxial cable, and optionally optical fiber cable, all placed in a star topology. Grade 2 cabling minimum requirements consist of two four-pair UTP cables and associated connectors that meet or exceed the requirements for Category 5e cabling; two 75-ohm coaxial and associated connectors at each telecommunications outlet and the DD; optionally, two-fiber optical fiber cabling. Installation of Category 6 cabling in place of Category 5e cabling is recommended.

The standard further dictates that a central location within a home or multitenant building be chosen at which to install a central cabinet or wall-mounted rack to support the wiring. This location should be close to the telephone company demarcation point and near the entry point of cable TV connections. Once the cabling system is installed, you can use it to connect phones, televisions, computers, cable modems, and EIA 6000-compliant home automation devices.