Category 5 cable

From Wikipedia, the free encyclopedia

Category 5 cable, commonly known as Cat 5, is a twisted pair cable type designed for high signal integrity. Many such cables are unshielded but some are shielded. Category 5 has been superseded by the Category 5e specification. This type of cable is often used in structured cabling for computer networks such as Ethernet, and is also used to carry many other signals such as basic voice services, token ring, and ATM (at up to 155 Mbit/s, over short distances).

1 Usage and wiring methods
2 See also
3 External links

Usage and wiring methods

Image:Rj45plug-8p8c.png

8P8C modular plug pin positioning

TIA/EIA-568-B T568A Wiring
Pin	Pair	Wire	Color
1	3	1	Image:Wire white green stripe.svg white/green
2	3	2	Image:Wire green.svg green
3	2	1	Image:Wire white orange stripe.svg white/orange
4	1	2	Image:Wire blue.svg blue
5	1	1	Image:Wire white blue stripe.svg white/blue
6	2	2	Image:Wire orange.svg orange
7	4	1	Image:Wire white brown stripe.svg white/brown
8	4	2	Image:Wire brown.svg brown

TIA/EIA-568-B T568B Wiring
Pin	Pair	Wire	Color
1	2	1	Image:Wire white orange stripe.svg white/orange
2	2	2	Image:Wire orange.svg orange
3	3	1	Image:Wire white green stripe.svg white/green
4	1	2	Image:Wire blue.svg blue
5	1	1	Image:Wire white blue stripe.svg white/blue
6	3	2	Image:Wire green.svg green
7	4	1	Image:Wire white brown stripe.svg white/brown
8	4	2	Image:Wire brown.svg brown

Image:CAT5e Cable.jpg

Image of partially stripped cable showing the twisted pairs.

Image:CAT-5E-Wall Outlet.jpg

Image of a Cat 5E Wall outlet showing the two wiring schemes: A for T568A, B for T568B.

Category 5

The original specification for category 5 cable was defined in ANSI/TIA/EIA-568-A, with clarification in TSB-95. These documents specified performance characteristics and test requirements for frequencies of up to 100 MHz.

Category 5 cable includes four twisted pairs in a single cable jacket. This use of balanced lines helps preserve a high signal-to-noise ratio despite interference from both external sources and other pairs (this latter form of interference is called crosstalk). It is most commonly used for 100 Mbit/s networks, such as 100BASE-TX Ethernet, although IEEE 802.3ab defines standards for 1000BASE-T - Gigabit Ethernet over category 5 cable. Cat 5 cable typically has three twists per inch of each twisted pair of 24 gauge copper wires within the cable.

Category 5e

Cat 5e cable is an enhanced version of Cat 5 that adds specifications for far end crosstalk. It was formally defined in 2001 in the TIA/EIA-568-B standard, which no longer recognizes the original Cat 5 specification. Although 1000BASE-T was designed for use with Cat 5 cable, the tighter specifications associated with Cat 5e cable and connectors make it an excellent choice for use with 1000BASE-T. Despite the stricter performance specifications, Cat 5e cable does not enable longer cable distances for Ethernet networks: cables are still limited to a maximum of 328 ft (100 m) in length (normal practice is to limit fixed ("horizontal") cables to 90 m to allow for up to 5 m of patch cable at each end). Cat 5e cable performance characteristics and test methods are defined in TIA/EIA-568-B.2-2001.

Connectors and other information

The cable exists in both stranded and solid conductor forms. The stranded form is more flexible and withstands more bending without breaking and is suited for reliable connections with insulation piercing connectors, but makes unreliable connections in insulation displacement connectors. The solid form is less expensive and makes reliable connections into insulation displacement connectors, but makes unreliable connections in insulation piercing connectors. Taking these things into account, building wiring (for example, the wiring inside the wall that connects a wall socket to a central patch panel) is solid core, while patch cables (for example, the movable cable that plugs into the wall socket on one end and a computer on the other) are stranded.

Cable types, connector types and cabling topologies are defined by TIA/EIA-568-B. Nearly always, 8P8C modular connectors, often incorrectly referred to as "RJ-45", are used for connecting category 5 cable.

The cable is terminated in either the T568A scheme or the T568B scheme. It doesn't make any difference which is used as they are both straight through (pin 1 to 1, pin 2 to 2, etc); however mixed cable types should not be connected in series as the impedance per pair differs slightly and could cause signal degradation. The article Ethernet over twisted pair describes how the cable is used for Ethernet, including special "cross over" cables.

External links

Cable your own house - written in 1999 and does have some out-of-date information.
Wiring up Cat 5
Ethernet pinout guide
Structured cabling instructions
How to wire your own Ethernet cables
Wiring telephones over structured cabling

Unshielded & Shielded Twisted Pair Cabling Standards

v • d • e</div>

Cat 1: Currently unrecognized by TIA/EIA. Previously used for POTS telephone communications, ISDN and doorbell wiring.
Cat 2: Currently unrecognized by TIA/EIA. Previously was frequently used on 4 Mbit/s token ring networks.
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.
Cat 4: Currently unrecognized by TIA/EIA. Provided performance of up to 20 MHz, and was frequently used on 16 Mbit/s token ring networks.
Cat 5: Currently unrecognized by TIA/EIA. Provided performance of up to 100 MHz, and was frequently used on 100 Mbit/s ethernet networks. May be unsuitable for 1000BASE-T gigabit ethernet.
Cat 5e: Currently defined in TIA/EIA-568-B. Provides performance of up to 100 MHz, and is frequently used for both 100 Mbit/s and gigabit ethernet networks.
Cat 6: Currently defined in TIA/EIA-568-B. It provides performance of up to 250 MHz, more than double category 5 and 5e.
Cat 6a: Future specification for 10 Gbit/s applications.
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. Designed for transmission at frequencies up to 600 MHz.