Category 5 cable

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Category 5 patch cable in T568B wiring

Category 5 cable, commonly referred to as cat 5, is a twisted pair cable for carrying signals. This type of cable is used in structured cabling for computer networks such as Ethernet. The cable standard provides performance of up to 100 MHz and is suitable for 10BASE-T, 100BASE-TX (Fast Ethernet), and 1000BASE-T (Gigabit Ethernet). Cat 5 is also used to carry other signals such as telephony 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.

Category 5 was superseded by the category 5e (enhanced) specification,[1] and later category 6 cable.

TIA/EIA-568-B.1-2001 T568A Wiring
Pin Pair Wire Color
1 3 1 Pair 3 Wire 1 white/green
2 3 2 Pair 3 Wire 2 green
3 2 1 Pair 2 Wire 1 white/orange
4 1 2 Pair 1 Wire 2 blue
5 1 1 Pair 1 Wire 1 white/blue
6 2 2 Pair 2 Wire 2 orange
7 4 1 Pair 4 Wire 1 white/brown
8 4 2 Pair 4 Wire 2 brown
TIA/EIA-568-B.1-2001 T568B Wiring[2]
Pin Pair Wire Color
1 2 1 Pair 2 Wire 1 white/orange
2 2 2 Pair 2 Wire 2 orange
3 3 1 Pair 3 Wire 1 white/green
4 1 2 Pair 1 Wire 2 blue
5 1 1 Pair 1 Wire 1 white/blue
6 3 2 Pair 3 Wire 2 green
7 4 1 Pair 4 Wire 1 white/brown
8 4 2 Pair 4 Wire 2 brown
Partially stripped cable showing the twisted pairs.
A cat 5e Wall outlet showing the two wiring schemes: A for T568A, B for T568B.

Cable standard[edit]

The specification for category 5 cable was defined in ANSI/TIA/EIA-568-A, with clarification in TSB-95.[3] These documents specify performance characteristics and test requirements for frequencies up to 100 MHz. Cable types, connector types and cabling topologies are defined by TIA/EIA-568-B. Nearly always, 8P8C modular connectors (often referred to as RJ45 connectors) 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.

Each of the four pairs in a cat 5 cable has differing precise number of twists per meter to minimize crosstalk between the pairs. Although cable assemblies containing 4 pairs are common, category 5 is not limited to 4 pairs. Backbone applications involve using up to 100 pairs.[4] This use of balanced lines helps preserve a high signal-to-noise ratio despite interference from both external sources and crosstalk from other pairs.

The cable is available in both stranded and solid conductor forms. The stranded form is more flexible and withstands more bending without breaking. Permanent 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.

The specific category of cable in use can be identified by the printing on the side of the cable.[5]

Bending radius[edit]

Most Category 5 cables can be bent at any radius exceeding approximately four times the outside diameter of the cable.[6][7]

Maximum cable segment length[edit]

The maximum length for a cable segment is 100 m per TIA/EIA 568-5-A.[8] If longer runs are required, the use of active hardware such as a repeater or switch is necessary.[9][10] The specifications for 10BASE-T networking specify a 100-meter length between active devices.[11] This allows for 90 meters of solid-core permanent wiring, two connectors and two stranded patch cables of 5 meters, one at each end.[12]

Category 5 vs. 5e[edit]

The category 5e specification improves upon the category 5 specification by tightening some crosstalk specifications and introducing new crosstalk specifications that were not present in the original category 5 specification.[13] The bandwidth of category 5 and 5e is the same (100 MHz)[14] and the physical cable construction is the same, and the reality is that most Cat5 cables meet Cat5e specifications, though it is not tested or certified as such.[15]


This type of cable is used in structured cabling for computer networks such as Ethernet over twisted pair. The cable standard provides performance of up to 100 MHz and is suitable for 10BASE-T, 100BASE-TX (Fast Ethernet), and 1000BASE-T (Gigabit Ethernet). 10BASE-T and 100BASE-TX Ethernet connections require two wire pairs. 1000BASE-T Ethernet connections require four wire pairs. Through the use of power over Ethernet (PoE), up to 25 watts of 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.[16]

Shared cable[edit]

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.[17][18][19][20][21] 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.[22]


Electrical characteristics for cat 5e UTP
Property Nominal Tolerance Unit ref
Characteristic impedance, 1-100 MHz 100 ± 15 Ω [23]
Characteristic impedance @ 100 MHz 100 ± 5 Ω [23]
DC loop resistance ≤ 0.188 Ω/m [23]
Propagation speed 0.64 c [23]
Propagation delay 4.80-5.30 ns/m [23]
Delay skew < 100 MHz < 0.20 ns/m [23]
Capacitance at 800 Hz 52 pF/m [23]
Inductance 525 nH/m [24]
Corner frequency[dubious ] ≤ 57 kHz [24]
Max tensile load, during installation 100 N [23]
Wire diameter 24 AWG (0.51054 mm ; 0.205 mm2) [23][25]
Insulation thickness 0.245 mm [23]
Maximum current per conductor 0.577 A [25]
Temperature operating -55 to +60 °C [23]
Maximum operating voltage
(PoE uses max 57 V DC)[26]
125 V DC [27]


Outer insulation is typically PVC or LSOH.

Example materials used as insulation in the cable[citation needed]
Acronym Material
PVC Polyvinyl Chloride
PE Polyethylene
FP Foamed polyethylene
FEP Teflon/fluorinated ethylene propylene
FFEP Foamed Teflon/fluorinated ethylene propylene
AD/PE Air dielectric/polyethylene


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.[28]

Individual twist lengths[edit]

By altering the length of each twist, crosstalk is reduced, without affecting the characteristic impedance.[dubious ] The distance per twist is commonly referred to as pitch. The pitch of the twisted pairs is not specified in the standard. Measurements on one sample of cat 5 cable yielded the following results.[29] Since the pitch of the various colors is not specified in the standard, pitch can vary according to manufacturer and should be measured for the batch being used if cable is being used in non-Ethernet situation where pitch might be critical.

   Pair color [cm] per turn Turns per [m]
Blue 1.38 72
Green 1.53 65
Orange 1.78 56
Brown 1.94 52

Environmental ratings[edit]

US & Canada fire certifications[30]
Class Phrase Standards
LSZH Communications Low Smoke Zero Halogen NES-711, NES-713, MIL-C-24643, UL-1685
CMP Communications Plenum CSA FT6[31] or NFPA 262 (UL 910)
CMR Communications Riser UL 1666
CMG Communications General purpose CSA FT4
CM Communications UL 1685 (UL 1581, Sec. 1160) Vertical-Tray
CMX Communications Residential UL 1581, Sec. 1080 (VW-1)
CMR (Communications Riser), insulated with high-density polyolefin and jacketed with low-smoke polyvinyl chloride (PVC).
CMP (Communications Plenum), insulated with fluorinated ethylene propylene (FEP) and polyethylene (PE) and jacketed with low-smoke polyvinyl chloride (PVC), due to better flame test ratings.
CM (Communications) is insulated with high-density polyolefin, but not jacketed with PVC and therefore is the lowest of the three in flame resistance.

Some cables are "UV-rated" or "UV-stable" meaning they can be exposed to outdoor UV radiation without significant destruction. The materials used for the mantle are usually PVC.[citation needed]

Any cable that contains air spaces can breathe in moisture, especially if the cable runs between indoor and outdoor spaces. Warm moist air can cause condensation inside the colder parts of the cable outdoors. It may be necessary to take precautions such as sealing the ends of the cables. Some cables are suitable for "direct burial", but this usually requires that the cable be gel filled in order to hinder moisture migration into the cable.

When using a cable for a tower, attention must be given to vertical cable runs that may channel water into sensitive indoor equipment. This can often be solved by adding a drip-loop at the bottom of the run of cable. If water enters the cable over a long time, for example a break in the outer shield due to wind movement fatigue, this can set up substantial head pressure within the cable. Water ingress at 28m can induce a pressure of 40 psi forcing water many meters along a horizontal run including back upwards. Therefore, it is imperative to maintain the integrity of the outer sheath on tall towers.[citation needed]

Plenum-rated cables are slower to burn and produce less smoke than cables using a mantle of materials like PVC. This also affects legal requirements for a fire sprinkler system. That is if a plenum-rated cable is used, sprinkler requirement may be eliminated.[32]

Shielded cables (FTP/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.

See also[edit]



  1. ^ "Voice and Data Cabling & Wiring Installations". Retrieved 2013-05-12. 
  2. ^ "ANSI/TIA/EIA-568-B.1-2001 Approved: April 12, 2001 ; Commercial Building Telecommunications Cabling Standard Part 1: General Requirements" (PDF).  090917
  3. ^ "Additional Transmission Performance Guidelines for 4-pair 100 v category 5 Cabling" (PDF). Retrieved 2013-05-12. 
  4. ^ As noted in ANSI/TIA/EIA-568-B-2 standard for backbone applications
  5. ^ "Ethernet Cable Identification and Use". Donutey. Retrieved 2011-04-01. 
  6. ^ "Selecting coax and twisted-pair cable". Electronic Products. 
  7. ^ "Category 5". Retrieved 2013-05-12. 
  8. ^ "The Evolution of Copper Cabling Systems from Cat5 to Cat5e to Cat6" (PDF). Panduit. 2004-02-27. Retrieved 2013-05-12. 
  9. ^ "UTP technology" (PDF). Extron Electronics. 2001. Retrieved 2013-05-12. 
  10. ^ "CAT5e Cable Wiring Schemes". B&B Electronics. Archived from the original on 2012-10-05. 
  11. ^ "IEEE Std 802.3-2008". Institute of Electrical and Electronics Engineers. 2008. Table 13-1 
  12. ^ "Horizontal Cabling". The Network Encyclopedia. Retrieved 2013-05-12. 
  13. ^ "UNDERSTANDING CAT - 5 CABLES" (PDF). Satelliete & Cable TV. Retrieved 2013-01-05"." 
  14. ^ "Cat5 Spec, cat6 specs, cat7 spec - Definitions, Comparison, Specifications". TEC Datawire. Retrieved 2013-01-05"." 
  15. ^ "Comparison between CAT5, CAT5e, CAT6, CAT7 Cables". 
  16. ^ "Transmitting video over CAT5 cable". EE Times. 2005-06-08. Retrieved 2013-12-07 
  17. ^ "Hack your House: Run both ethernet and phone over existing Cat-5 cable". Retrieved 2013. 
  18. ^ ZyTrax. "LAN and Telephones". quote: "Since 10base-T or 100base-TX wiring uses 2 pairs (4 wires) and each analog phone connection uses a single pair (2 wires) you can, subject to limitations, run 2 telephone connections and LAN traffic on category 5(e) wiring"
  19. ^ Siemon. "Cable Sharing in Commercial Building Environments: Reducing Cost, Simplifying Cable Management, and Converging Applications onto Twisted-Pair Media". retrieved 2014-04-28.
  20. ^ "RJ45/RJ11 Network Cable Splitters for Ethernet and Phone Line Sharing". quote: "carry one old fashioned analog telephone signal and one 10/100Mbps Ethernet signal by the same single network cable."
  21. ^ "ATS 10/100 Base T Splitter Adapters". Retrieved 2014-08-17. 
  22. ^ "HDBaseT Alliance Shows the Future of Connected Home Entertainment at CES 2013" (PDF). News release. January 9, 2013. Retrieved June 5, 2013. 
  23. ^ a b c d e f g h i j k "SuperCat OUTDOOR CAT 5e U/UTP" (PDF). Archived from the original (PDF) on 2012-03-16. 
  24. ^ a b "Transmission Line Zo". 
  25. ^ a b "Wire Gauge and Current Limits Including Skin Depth and Strength". PowerStream. Retrieved 2013-05-12. 
  26. ^ IEEE 802.3at-2009 Table 33-11
  27. ^ "Copper Data Cables" (PDF). p. 6. Archived from the original (PDF) on 2006-06-25. 
  28. ^ "ANSI/TIA/EIA-568-B.2-2001, Commercial Building Telecommunications Cabling Standard" (PDF). p. 6 ¶4.3.2. 
  29. ^
  30. ^ "Technical Information" (PDF). Belden. p. 22.20. Archived from the original (PDF) on 2012-03-03. 
  31. ^ "CSA Flame Test Ratings". Retrieved 2013-05-12. 
  32. ^ "What are the differences between PVC, riser and plenum-rated cables?". Retrieved 2009-01-26.