CAT5 (Category 5) is an ethernet network cable standard that describes the physical characteristics of the wiring used to carry data along digital networks. CAT5 cable is made up of 4 twisted pairs of unshielded wires encased in a polyethylene sheath. A completed cable will have a RJ-45 plug at each end.
The outer sheath of CAT5 cable is generally blue, but can be any color, “CAT5″ will be printed on the outer sheathing to indicate its certification. Each separate wire inside is also sheathed in plastic with a standard color scheme.
The technology behind this standard is referred to as “unshielded twisted pair” in that a pair of unshielded wires are twisted together to cancel out electromagnetic interference.
There are 4 different color pairs and in order to minimise crosstalk interference, the interval between the twists of each color pair is slightly different.
CAT5 Table
The cable is terminated in either the T568A scheme or the T568B scheme. Canada uses the T568A standard and the United States commonly uses T568B scheme. It really doesn’t make any difference which is used as long as you use only one of the standards so all connections are the same at your location to avoid confusion and potential problems. Mixed cable types should not be connected in series as the impedance per pair differs slightly and may cause signal degradation.
History
Work began on developing a telecommunications cabling standard in 1985. In 1987, equipment was being manufactured that could use twisted pair telephone cable for data communication, and in 1991, the first standard was published for CAT3 cabling, which is what is still used for most voice (telephone) communications today. The standards for CAT4 and CAT5 were released later in 1991. It wasn’t until 2001 that the standard for CAT5e was released.
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Cat 1: Currently not recognized by TIA/EIA. Previously used for POTS (plain old telephone system) telephone communications, ISDN and doorbell wiring.
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Cat 2: Currently not recognized by TIA/EIA. Previously was frequently used on 4 Mbit/s token ring networks.
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Cat 3: Currently defined in TIA/EIA-568-B, used for data networks using frequencies up to 16 MHz. Historically popular for 10 Mbit/s Ethernet networks.
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Cat 4: Currently not recognized by TIA/EIA but originally defined in TIA/EIA-568-A. Defined up to 20 MHz, and was frequently used on 16 Mbit/s token ring networks.
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Cat 5: Currently not recognized by TIA/EIA but originally defined in TIA/EIA-568-A. Defined up to 100 MHz, and was frequently used on 100 Mbit/s Ethernet networks. May be unsuitable for 1000BASE-T gigabit ethernet.
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Cat 5e: Currently defined in TIA/EIA-568-B. Defined up to 100 MHz, and is frequently used for both 100 Mbit/s and 1000BASE-T Gigabit Ethernet networks.
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Cat 6: Currently defined in TIA/EIA-568-B. Defined of up to 250 MHz, more than double category 5 and 5e.
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Cat 6a: Currently defined in ANSI/TIA/EIA-568-B.2-10. Provides performance of up to 500 MHz, double that of category 6. Suitable for 10GBase-T.
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Cat 7: An informal name applied to ISO/IEC 11801 Class F cabling. This standard specifies four individually-shielded pairs (STP) inside an overall shield. Defined up to 600 MHz.
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Cat 7a: An informal name applied to Amendment 1 of ISO/IEC 11801 Class F cabling. Defined up to 1000 MHz.
Final Word
For your home network where the cables are not being installed in the walls, CAT5e is the way to go unless all of your network components are rated for Gigabit speeds. If they are, you may see the benefit of using CAT6 cables. If you are completely wiring or re-wiring your home, you should go with CAT6 cable to make sure that it will meet your future performance needs.
/steve
A 
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