Uncle Ted's Guide To
VDV (voice/data/video) Cabling
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Structured Cabling for VDV Communications - An Overview

A Little History....

The history of telecommunications spans a mere 150 years, starting with the development of the telegraph in the early 19th century. Telegraphy gave man the means to transmit impulses that represent letters. When these letters were received and decoded, they provided a way to convey messages over long distances.
 
Naturally, the next step was to consider whether sound might also somehow be electrically transmitted. Alexander Graham Bell applied for his patent for an "electrical speaking telephone" om 1876. In reality, many men contributed to telephone improvements including David Edward Hughes whose invention of the microphone became universally used in telephones.
 
It is amazing how quickly the use of the telephone spread. The first switchboard, an experiment, was installed in Boston in 1877. Just four years later, there were 54,000 telephones in the United States! In the first decade of the 20th century, Dr. Lee deForest's invention of the vacuum tube amplifier enabled long distance communications.
 
By the 1970s, integrated circuit technology and the microprocessor began to influence telecommunications and computers. Experiments began in digital voice transmission and fiber optics. Computer networks like Ethernet and the predecessor of the Internet were developed.
 
The 1980s brought wide scale use of digital telecom, computer networks and fiber optics, but was also the era of the breakup of the Bell system. Users who once depended on AT&T for telecom standards and IBM or other computer companies for the "rules" they depended on were left stranded.
 
Manufacturers took up standards development to insure interoperability of their products - under the auspices of the IEEE for computer networking electronics and EIA/TIA for cabling. Thus was born the industry standards that we all depend on for today's communications networks.
 
 
Mandatory or Voluntary Standards?
 
Widespread useage of any technology depends on the existence of acceptable standards. The most important standard and the only one that is mandatory is the National Electrical Code developed by the National Fire Protection Assn. that covers all aspects of electrical safety. Article 800 of the NEC covers communication circuits, such as telephone systems and outside wiring for fire and burglar alarm systems and Article 770 covers fiber optics. Also, all VDV wiring must comply with building and electrical codes applicable in your state or city.
 
But during the 1980s, phone signals became digital, LANs proliferated and new cables and cabling architecture were needed. The goal was to make buildings "smart," able to allow computer and phone conversations over a standardized wiring system. By the early 90s, a scheme of "structured cabling" was standardized by technical committee of a trade association, the merged Electronic Industries Association and Telecommunications Industry Association (hereafter referred to as EIA/TIA).
 
Just to confuse everybody, this cabling standard, developed by the EIA/TIA TR 41.8 committee - now renamed TR 42, is referred to by the number of the primary standard, EIA/TIA 568, although there are actually a number of standards, technical advisories, etc. that cover all aspects of structured cabling. We'll go along with the crowd and simply say "568" when we generally mean the entire output of the TR 42 committee!
 
And to further confuse everybody, many people think this standard is a mandatory, even legal, document like the NEC. NO WAY! "568" is a voluntary interoperability standard for communications cabling, developed by a number of manufacturers of cabling components and networking equipment, so that they might make equipment that could use any 568-compliant cabling system and be upgraded in the future as long as it was designed for the same cable plant.
 
What 568 is, in fact, is a common sense approach to cabling that offers interoperability, upgradability and low cost due to the numerous manufacturers offering compatible products. But it ain't code!
 
Note: TIA-568 is a US standard. Overseas, ISO/IEC writes the standards and a summary of their standards is below.
The Basics of "568"
 
"568" calls for connecting the desktop (work area) to a telecom closet (the "horizontal" run) with up to 100 meters of cable (including no more than 10 m total of patchcords), which is usually Cat 3, Cat 5 or Cat5e UTP. The "Cat" or category designation refers to a performance grade, which we will explain later in the Cables section. Most copper installations today use Cat 5e or Cat 6 exclusively, as it isn't that much more expensive than Cat 3 and can support phones or any LAN on any outlet.
 
 
The backbone cabling can be either UTP or fiber optics. In larger networks, fiber is most often used for its longer distance capability and higher bandwidth. 568 specifies two multimode fibers, 62.5/125 - the most common MM fiber in recent history, and 50/125 - a higher bandwidth fiber rated for use with lasers for gigabit networks that is rapidly overtaking 62.5/125 in popularity. Singlemode fiber is also specified for longer links, as in a campus, for high speed networks.
 
Fiber optics is also a horizontal option in 568, but not often used because of the higher cost except where high bitrate networks or future upgrades are expected. However, a properly designed centralized fiber network that connects the desktop directly to the computer room with no intermediate electronics does not need a telecom closet and saves the cost of conditioned power, data ground, AC and the floor space, which may offset the additional cost of the fiber electronics.
 
Virtually every network now includes wireless, which is, of course, not wireless-access points are connected into the network with copper or fiber cabling.
The telecom closet houses the hubs for the computers in the work areas. These hubs are interconnected on "backbone" wiring which is mostly fiber optics, as it usually carries higher speed signals over longer distances and provides isolation from ground loops, another bugaboo of LANs. The main cross-connect (MXC) or equipment room contains the network and telco hardware. For the telephones, their lower bandwidth requirements allow longer runs, so they are usually simply connected to backbone cables in the telecom closet with a punchdown and run straight to the MXC.
 
568 also includes IBM Type 1 cable, a shielded two pair cable, since it is still used in some networks. However, it ignores coax cable, like RG-58 used in some Ethernet LANs and RG-6 used in CATV and CCTV.
 
Beyond 568
568 is only part of the structured cabling standards. It's a multi-part standard itself and there are several more standards cover other areas of cabling:
EIA/TIA 568: The main standard document for structured cabling, usually referred to as simply "568." It is now on the "B" revision and includes sections for general specifications (B.1) and individual sections for copper (B.2) and fiber optics (B.3)
EIA/TIA 569 A: Covers pathways and spaces. Defines the "telecom closet" or telecom room as it is now called.
EIA/TIA 570 A: For residential cabling.
EIA/TIA 606: Cabling system administration (documentation)
EIA/TIA 607: Grounding and bonding
 
 
International Standards
 
The international equivalent of EIA/TIA 568 is ISO/IEC 11801. The standards are written similarly to what has been done by TR 42. Here are their relevant standards:
ISO/IEC 11801 - Cabling for customer premises
ISO/IEC 14763-1 - Administration, documentation
ISO/IEC 14763-2 - Planning and Installation
ISO/IEC 14763-3 - Testing optical fibre cabling
IEC 61935-1 - Testing copper cabling
 
 
Learning More About Standards
There are a number of ways of finding out more about these cabling standards. You can buy a complete copy of the EIA/TIA or ISO/IEC standards from Global Engineering Documents for a lot of money and wade through the strange standards language. Or you can get catalogs from a number of companies that sell cabling products who have extremely complete explanations of the standards. Guess which we recommend?!
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