Generic Building-Cabling Standards

If you are planning any data communications link for use between pieces of equipment inside a building, or between buildings on a single campus, you need to know about generic building-cabling standards [64] , [65] . In your application, these standards will

1. Save you money,
2. Shorten your development cycle, and
3. Make it possible for customers to install your product.

Compliance with generic building-cabling standards saves you money, because generic cabling components are cheap . These components are cheap because they are standardized and produced in high volumes . For example, there are today more than 100 million Ethernet nodes installed and operating on generic building cabling. [60] [63]

[60] This chapter is adapted from Fast Ethernet: Dawn of a New Network .

Compliance shortens your development time because it limits your choices. For example, there are 74 different types of U.S. MIL-SPEC 50-ohm coaxial cables. Picking the right one is a nightmare. There are only a handful of popular varieties of unshielded twisted-pair generic building cabling.

Compliance makes it possible for customers to install your product. One hundred percent of MIS managers in Fortune 500 companies equip their buildings with standard, generic building cabling. Other types of cable are not generally available in these buildings and in some cases are not permitted to enter the building .

The international specifications for voice and data cabling are a boon not only to designers of LAN and telephone equipment, but to anyone contemplating the use of cables for any digital application, as long as you stick with the standard parts . This chapter introduces you to the building-cabling standards and shows you where to go for more information.

The world of building cabling has not always been clearly defined. Prior to 1985, each data communication standard mandated its own, unique type of cabling. When you bought new equipment, you put in new cabling. As a result, conduits overflowed with different kinds of coax, twin-ax, tri-ax, multiwire, quad, twisted-pair, and fiber- optic cables. Users accepted this sorry state of affairs by rationalinzing that the cost of new cables was only a small part of the cost of the new computers and communciation services they were buying.

Today, LAN interface cards sell for a fraction of the cost of cabling a new office. Installation of new cabling is no longer acceptable. Customers demand systems that use the existing cables already in the walls. The key buzzword here is generic cabling . Any system that connects from room to room, or from building to building, should use generic cabling.

Generic cabling is defined by two standards:

1. In North America: TIA/EIA 568-B.1-2001
2. In other countries : ISO/IEC 11801:2002

These standards specify the preferred cables, preferred methods of installation, and preferred topologies for three popular types of building cabling: 100- W balanced cabling, multimode fiber, and single-mode fiber. The scope of both standards includes data and telephone cabling, but not wiring for power, HVAC, or building control systems. Building architects around the world are currently designing new structures according to these standards, which provide much needed wiring-closet space within 100 m of every desktop location.

The best place to purchase cabling standards is from an independent technical-standards warehouse. Both these services take credit cards and ship overnight:

• Global Engineering, http://global.ihs.com , (800) 854-7179 (U.S. toll free).
• Techstreet, http://www.techstreet.com , (800) 699-9277 (U.S. toll free).

Each standard references a slew of other documents, all of which have been modified many times by various addenda and changes. I can't possibly list all the pieces here because building-cabling standards change so often. When ordering standards, always ask for the latest complete package, including all the detailed cabling specifications for both copper and fiber. Then ask if there are any outstanding drafts or revisions being prepared. The standards organizations that develop these documents are sometimes reluctant to inform you about anything other than complete, finalized standards, but the independent technical-standards warehouses are usually happy to ship copies of the latest drafts-in-progress. In some cases you may have to ask the standards organization how to contact or join the relevant technical working committee in order to obtain copies of drafts-in-progress. I can't overemphasize the importance of developing your own direct link into the standards process. That's how you predict the future.

The TIA/EIA and ISO/IEC standards are similar, but not identical. For example, definitions of critical terms in the two documents are inexplicably different. For the most part, they agree on these major points:

• A star-wiring topology is good,
• The maximum distance from each desktop to the telecommunications room should be no more than 100 m, and
• 100- W balanced cabling or fiber are the preferred means of connection.

All new systems should be designed to work with the TIA/EIA standard, the ISO/IEC standard, or the common ground between the two .

As a system developer, which standard should you pick? This depends on your market. The two standards emerged from different organizations, with different charters , for different purposes.

The TIA/EIA cabling standard was begun in 1985 by the Electronic Industries Association. In 1988, portions of the EIA broke away to merge with the Telecommunications Industry Association (TIA). Thereafter, this building cabling standard has been loosely called TIA/EIA 568 . The exact latest version is TIA/EIA 568-B.1-2001 . The TIA/EIA technical committees are dominated by U.S. and Canadian companies. They produce standards relevant for use in North America.

The International Organization for Standardization (ISO) developed its cabling standards separately through a joint technical relationship with the International Electrotechnical Commission (IEC). Their latest building cabling document is called ISO/IEC 11801:2002 . ISO standards take into account international considerations, such as the demand for screened cables in Europe.

During the past few cycles of standardizing, the TIA and ISO documents have merged almost seamlessly. Few substantive differences remain .

The safest choice for most system manufacturers is the common ground between the two standards. For example, unless you really need the bandwidth, you should shy away from category 7 cabling, which is endorsed by ISO/IEC 11801:2002 but not by TIA/EIA 568-B.1-2001 .

POINTS TO REMEMBER

• Any system that connects from room to room, or from building to building, should use generic building cabling.
• Building-cabling standards are evolving rapidly . If you want the latest information, order the latest standards.