Category 5 cable

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Partially stripped cable showing the four twisted pairs (eight wires) CAT5e Cable.jpg
Partially stripped cable showing the four twisted pairs (eight wires)

Category 5 cable (Cat 5) is a twisted pair cable for computer networks. Since 2001, the variant commonly in use is the Category 5e specification (Cat 5e). The cable standard provides performance of up to 100 MHz and is suitable for most varieties of Ethernet over twisted pair up to 2.5GBASE-T [1] [2] [3] [4] but more commonly runs at 1000BASE-T (Gigabit Ethernet) speeds. Cat 5 is also used to carry other signals such as telephone and video.


This cable is commonly connected using punch-down blocks and modular connectors. Most Category 5 cables are unshielded, relying on the balanced line twisted pair design and differential signaling for noise rejection.


The specification for category 5 cable is defined in ISO/IEC 11801, IEC 61156 and EN 50173.

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

The cable is available in both stranded and solid conductor forms. The stranded form is more flexible and withstands more bending without breaking. Patch cables are stranded. Permanent wiring used in structured cabling is solid-core. The category and type of cable can be identified by the printing on the jacket. [6]

The category 5 specification requires conductors to be pure copper. The industry has seen a rise in non-compliant / counterfeit cables, especially of the Copper Clad Aluminum (CCA) variety. [7] This has exposed the manufacturers or installers of such fake cable to legal liabilities. [8]

Variants and comparisons

The category 5e specification improves upon the category 5 specification by revising and introducing new specifications to further mitigate the amount of crosstalk. [9] The bandwidth (100 MHz) and physical construction are the same between the two, [10] and most Cat 5 cables actually meet Cat 5e specifications, though they are not specifically certified as such. [11] The category 5 was deprecated in 2001 and superseded by the category 5e specification. [12]

The Category 6 specification improves upon the Category 5e specification by extending frequency response and further reducing crosstalk. The improved performance of Cat 6 provides 250 MHz bandwidth. [12] Category 6A cable provides 500 MHz bandwidth. Both variants are backwards compatible with Category 5 and 5e cables.


TIA/EIA-568-B.1-2001 T568A Wiring
131 Wire white green stripe.svg white/green
232 Wire green.svg green
321 Wire white orange stripe.svg white/orange
412 Wire blue.svg blue
511 Wire white blue stripe.svg white/blue
622 Wire orange.svg orange
741 Wire white brown stripe.svg white/brown
842 Wire brown.svg brown
TIA/EIA-568-B.1-2001 T568B Wiring [13]
121 Wire white orange stripe.svg white/orange
222 Wire orange.svg orange
331 Wire white green stripe.svg white/green
412 Wire blue.svg blue
511 Wire white blue stripe.svg white/blue
632 Wire green.svg green
741 Wire white brown stripe.svg white/brown
842 Wire brown.svg brown
A Cat 5e wall port showing the two wiring schemes: A for T568A, B for T568B CAT-5E-Wall Outlet.jpg
A Cat 5e wall port showing the two wiring schemes: A for T568A, B for T568B
Category 5 patch cable in T568B wiring Cat 5.jpg
Category 5 patch cable in T568B wiring

Cable types, connector types and cabling topologies are defined by ANSI/TIA-568. Nearly always, 8P8C modular connectors (often referred to incorrectly as RJ45 connectors [14] [15] [16] ) are used for connecting category 5 cable. The cable is terminated in either the T568A scheme or the T568B scheme. The two schemes work equally well and may be mixed in an installation so long as the same scheme is used on both ends of each cable.


Category 5 cable is used in structured cabling for computer networks such as Ethernet over twisted pair. The cable standard prescribes performance parameters for frequencies up to 100 MHz and is suitable for 10BASE-T , 100BASE-TX (Fast Ethernet), 1000BASE-T (Gigabit Ethernet), 2.5GBASE-T , and 5GBASE-T . 10BASE-T and 100BASE-TX Ethernet connections require two wire pairs. 1000BASE-T and faster Ethernet connections require four wire pairs. Through the use of power over Ethernet (PoE), power can be carried over the cable in addition to Ethernet data.

Cat 5 is also used to carry other signals such as telephony and video. [17] In some cases, multiple signals can be carried on a single cable; Cat 5 can carry two conventional telephone lines as well as 100BASE-TX in a single cable. [18] [19] [20] [21] [22] The USOC/RJ-61 wiring standard may be used in multi-line telephone connections. Various schemes exist for transporting both analog and digital video over the cable. HDBaseT (10.2 Gbit/s) is one such scheme. [23]


The use of balanced lines helps preserve a high signal-to-noise ratio despite interference from both external sources and crosstalk from other pairs.

Electrical characteristics for Cat 5e UTP
Property Nominal ToleranceUnitref
Characteristic impedance , 1–100 MHz 100± 15 Ω [24]
Characteristic impedance @ 100 MHz100± 5Ω [24]
DC loop resistance ≤ 0.188Ω/m [24]
Propagation speed relative to the speed of light 0.641 [24]
Propagation delay 5.30 ns/m [24]
Delay skew < 100 MHz< 0.20ns/m [24]
Capacitance at 800 Hz52 pF/m [24]
Max tensile load, during installation100 N [24]
Wire diameter (24 AWG; 0.205 mm2))0.51mm [24]
Operating temperature−55 to +60°C [24]
Maximum DC operating voltage
( PoE uses max 57 V) [25]
125 V [26]


Outer insulation is typically polyvinyl chloride (PVC) [27] or low smoke zero halogen (LS0H)[ citation needed ].

Example materials used as insulation in the cable [28]
PE Polyethylene
FPFoamed polyethylene
FEP Fluorinated ethylene propylene
FFEPFoamed fluorinated ethylene propylene
AD/PEAir dielectric/polyethylene
LSZH or LS0HLow smoke, zero halogen
LSFZH or LSF0HLow smoke and fume, zero halogen

Bending radius

Most Category 5 cables can be bent at any radius exceeding approximately four times the outside diameter of the cable. [29] [30]

Maximum cable segment length

The maximum length for a cable segment is 100 metres (330 ft) per TIA/EIA 568-5-A. [31] If longer runs are required, the use of active hardware such as a repeater or switch is necessary. [32] [33] The specifications for 10BASE-T networking specify a 100-meter length between active devices. [34] This allows for 90 meters of solid-core permanent wiring, two connectors and two stranded patch cables of 5 meters, one at each end. [35]


Since 1995, solid-conductor UTP cables for backbone cabling is required to be no thicker than 22 American Wire Gauge (AWG) and no thinner than 24 AWG, or 26 AWG for shorter-distance cabling. This standard has been retained with the 2009 revision of ANSI TIA/EIA 568. [36]

Although cable assemblies containing 4 pairs are common, category 5 is not limited to 4 pairs. Backbone applications involve using up to 100 pairs. [37]

Individual twist lengths

The distance per twist is commonly referred to as pitch. Each of the four pairs in a Cat 5 cable has differing precise pitch to minimize crosstalk between the pairs. The pitch of the twisted pairs is not specified in the standard. Measurements on one sample of Cat 5 cable yielded the following results. [38]

  Pair color[cm] per turnTurns per [m]

Since the pitch of the various colors is not specified in the standard, pitch can vary and should be measured for the batch being used if the cable is being used in a non-Ethernet situation where pitch may be critical.

Environmental ratings

United States and Canada fire certifications [39]
LSZHCommunications low-smoke zero halogenNES‑711, NES‑713, MIL‑C‑24643, UL 1685
CMPCommunications plenumInsulated with fluorinated ethylene propylene (FEP) and polyethylene (PE) and jacketed with low-smoke polyvinyl chloride (PVC), due to better flame test ratings. CSA  FT6 [40] or NFPA  262 (UL  910)
CMRCommunications riserInsulated with high-density polyolefin and jacketed with low-smoke polyvinyl chloride (PVC).

UL  1666

CMGCommunications general purposeCSA FT4
CMCommunicationsInsulated with high-density polyolefin, but not jacketed with PVC and therefore is the lowest of the three in flame resistance.UL 1685 (UL 1581, Sec. 1160) Vertical-Tray
CMXCommunications residentialUL 1581, Sec. 1080 (VW-1)

Some cables are "UV-rated" or "UV-stable" meaning they can be exposed to outdoor UV radiation without significant degradation.[ citation needed ]

Plenum-rated cables are slower to burn and produce less smoke than cables using a mantle of materials like PVC. Plenum-rated cables may be installed in plenum spaces where PVC is not allowed. [41] [ self-published source? ]

Shielded cables (FTP or STP) are useful for environments where proximity to RF equipment may introduce electromagnetic interference, and can also be used where eavesdropping likelihood should be minimized.

Related Research Articles

Ethernet over twisted pair Ethernet physical layers using twisted-pair cables

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Fast Ethernet Ethernet standards that carry traffic at the nominal rate of 100 Mbit/s

In computer networking, Fast Ethernet physical layers carry traffic at the nominal rate of 100 Mbit/s. The prior Ethernet speed was 10 Mbit/s. Of the Fast Ethernet physical layers, 100BASE-TX is by far the most common.

Gigabit Ethernet

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Category 3 cable, commonly known as Cat 3 or station wire, and less commonly known as VG or voice-grade, is an unshielded twisted pair (UTP) cable used in telephone wiring. It is part of a family of standards defined jointly by the Electronic Industries Alliance (EIA) and the Telecommunications Industry Association (TIA) and published in TIA/EIA-568-B.

StarLAN was the first IEEE 802.3 standard for Ethernet over twisted pair wiring. It was standardized by the standards association of the Institute of Electrical and Electronics Engineers (IEEE) as 802.3e in 1986, as the 1BASE5 version of Ethernet. The StarLAN Task Force was chaired by Bob Galin.

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Registered jack Telecommunication network interface

A registered jack (RJ) is a standardized telecommunication network interface for connecting voice and data equipment to a service provided by a local exchange carrier or long distance carrier. Registration interfaces were first defined in the Universal Service Ordering Code (USOC) system of the Bell System in the United States for complying with the registration program for customer-supplied telephone equipment mandated by the Federal Communications Commission (FCC) in the 1970s. They were subsequently codified in title 47 of the Code of Federal Regulations Part 68. Registered Jack connections began to see use after their invention in 1973 by Bell Labs. The specification includes physical construction, wiring, and signal semantics. Accordingly, registered jacks are primarily named by the letters RJ, followed by two digits that express the type. Additional letter suffixes indicate minor variations. For example, RJ11, RJ14, and RJ25 are the most commonly used interfaces for telephone connections for one-, two-, and three-line service, respectively. Although these standards are legal definitions in the United States, some interfaces are used worldwide.

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