| CATEGORY 5 CABLING
In theory, there are several classifications of copper cabling systems available for data communication applications today. In fact, the EIA/TIA-568A standard1 defines five categories or types of copper cable and components:
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Category 3
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16 MHz
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100 ohm unshielded twisted pair
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Category 4
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20 MHz
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100 ohm unshielded twisted pair
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Category 5
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100 MHz
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100 ohm unshielded twisted pair
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Type 1
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20 MHz
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150 ohm shielded twisted pair
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Type 1A
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300 MHz
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150 ohm shielded twisted pair
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Category 5 cable is constructed using eight 24 AWG insulated conductors (four pairs), enclosed by a thermoplastic jacket. Each of the four conductor pairs is twisted together at a slightly balanced high-speed communications circuit and to reject electrical interference or "noise" from sources such as power wiring, fluorescent and HID ballasts, motors, and so on.
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The reality, however, is that only one - Category 5 - is in widespread use at this time. In fact, Cat 5 has become synonymous with copper (as opposed to optical fiber) teledata systems.
The reason is simple: speed.
Category 3 cabling, at just 16 MHz, was originally intended for slower computer networking protocols like old-style Ethernet. But as data applications speeded up, Cat 3 soon became too slow for anything but voice telephone communications.
Rather than moving up to the next level of bandwidth - the 20 MHz Category 4 system - most data network specifies and users jumped directly to Category 5 for significantly greater speed. As a result, no Cat 4 cable has been seen out in the real world for a couple of years now.
What's more, as prices for Cat 5 cable and components have dropped, many installers now use Cat 5 for all voice systems as well as data systems, virtually eliminating Cat 3 from the market.
Type 1 and 1A, meanwhile, are special-purpose four-conductor cables designed for particular computer network protocols. They have never achieve widespread acceptance.
GETTING EVER FASTER
Just as speed has made Cat 5 the de facto standard for data networks, it has driven manufacturers to develop and market "extended performance" Cat 5 cables. These cables - which are manufactured with tighter twisted, more precise conductor-to-conductor spacing, and premium insulation - are rated at 350 MHz. But because there are no extended performance Cat 5 outlets and patch panels to connect to these premium cables, there are no guarantees the resulting system can perform at that rating.
1 EIA/TIA-568A, the Commercial Building Telecommunications Cabling Standard, is the fundamental standard for telecom/LAN wiring. It defines the basic cable and outlet performance categories (Cat 3, 4, and 5 copper, plus optical fibers) as well as "horizontal" and "backbone" cabling. In addition, this standard requires teledata wiring to be installed in a star or radial configuration, with homeruns from every outlet. |
