Recently, I read several articles about premises cabling in which the authors called unshielded twisted-pair (UTP) cabling “Cat 5,” even though, over the last 20 years, we’ve seen UTP developed into enhanced Category 5 (Cat 5e), Cat 6, augmented Cat 6 (Cat 6a) and even the (maybe) future standard for Cat 7. “Cat 5” is like that embarrassing nickname you had in elementary school that you want to forget, but some old friends still call you by it! Well, Sparky, let’s see if you have “Cat 5” straight! Correct answers and explanations are in red.
1. Cat 5 was not the first category-rated UTP cable. That honor goes to _________.
A. Cat 1
B. Cat 2
C. Cat 3
D. Cat 4
Cat 3 was the first standardized UTP cable under TIA-568.
2. Premises cabling standards, commonly called TIA-568, were written to ensure _________.
A. Cabling performance
B. Component interoperability
C. Operation with standardized communications systems
D. All of the above
TIA-568 standards are written to cover all these needs of the communications market.
3. The TIA standards for category-rated UTP cable (TIA-568) were derived from _________.
A. AT&T studies in the early 1980s
B. The Anixter Levels cable-rating system
C. IBM cabling systems
D. DECnet standards
Anixter developed their levels program so their customers could compare UTP cables. They allowed TIA to adopt their system under the name “Category.”
4. Cat 3 UTP was created for use with _________.
A. POTS (plain old telephone service)
C. 10BASE-T (10 Mbps Ethernet)
D. 100BASE-T (100 Mbps Ethernet)
Cat 3, the first category-rated UTP cable, was developed for the first Ethernet standard for UTP cable, 10Base-T.
5. Cat 4 UTP cable was introduced for higher speed networks but was replaced by a higher performance version months after introduction.
Cat 4 was introduced for a new version of IBM Token Ring which never gained acceptance and was dropped in favor of Cat 5.
6. Cat 5 UTP was needed for UTP to be used with _________.
A. 10BASE-T (10 Mbps Ethernet)
B. 100BASE-T (100 Mbps Ethernet)
C. 1000BASE-T (Gbps Ethernet)
“Fast” Ethernet at 100 Mb/s required a higher bandwidth UTP cable, leading to the development of Cat 5.
7. To upgrade Cat 5 for gigabit Ethernet, it was necessary to add new specifications for delay skew and crosstalk, creating a new cable type called _________.
A. Cat 5e (enhanced Cat 5)
B. Cat 5+ (augmented Cat 5)
C. Cat 6
D. It was still just called Cat 5
GbE used all four pairs of a UTP cable in both directions simultaneously, requiring several new performance perameters.
8. Cat 6 was too high-performance for gigabit Ethernet and too low for 10G Ethernet.
Between GbE and 10GbE, technology in networking moved faster than cabling technology and Cat 6 became a “cable without a network.”
9. Cat 6a, which is required for 10G Ethernet, requires cables so precisely made that _________.
A. They must be factory-terminated
B. They no longer work with modular 8-pin connectors (aka RJ-45)
C. Wires in each pair must be smaller conductors
D. Crosstalk from one cable to another can be a problem
Cat 6A cables have pairs so precisely wound that crosstalk can occur from one cable to another run in the same cable tray.
10. Cat. 7, the cable not recognized in current TIA-568 standards but used in Class F systems internationally, differs from earlier category-rated cables in that _________.
A. Each pair and the entire cable are shielded
B. Each pair is a small coaxial cable
C. A foil shield is added around the entire cable
D. The jacket is thicker and made of a conductive plastic
Cat 7 cable is a shielded cable with shields around each pair and the cable as a whole to prevent crosstalk at frequencies up to 1000 MHz.
HAYES is a VDV writer and educator and the president of The Fiber Optic Association. Find him at www.jimhayes.com.