Category 5 cable (Cat 5) is atwisted pair cable forcomputer networks. Since 2001, the variant commonly in use is theCategory 5e specification (Cat 5e). The cable standard provides performance of up to 100 MHz and is suitable for most varieties ofEthernet over twisted pair up to2.5GBASE-T[1][2][3][4] but more commonly runs at1000BASE-T (Gigabit Ethernet) speeds. Cat 5 is also used to carry other signals such astelephone andvideo.
This cable is commonly connected usingpunch-down blocks andmodular connectors. Most Category 5 cables areunshielded, relying on thebalanced line twisted pair design anddifferential signaling for noise suppression.
Category 5 is currently defined inISO/IEC 11801,IEC 61156 andEN 50173, though it was originally defined inANSI/TIA/EIA-568-A (with clarification in TSB-95).[5] These documents specify performance characteristics and test requirements forfrequencies 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 instructured cabling is solid. 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. There has been a rise in counterfeit cables, especially of the copper-clad aluminum (CCA) variety.[7] This has exposed the manufacturers and installers of such fake cable to legal liabilities.[8]
The Category 5e specification improves upon the Category 5 specification by further mitigatingcrosstalk.[9] Thebandwidth (100 MHz) and physical construction are the same between the two,[10] and most Cat 5 cables actually happen to meet Cat 5e specifications even though they are not certified as such.[11] Category 5 was deprecated in 2001 and superseded by the Category 5e specification.[12]
TheCategory 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 arebackward compatible with Category 5 and 5e cables.
| Pin | Pair | Wire | Color |
|---|---|---|---|
| 1 | 3 | 1 |  white/green |
| 2 | 3 | 2 |  green |
| 3 | 2 | 1 |  white/orange |
| 4 | 1 | 2 |  blue |
| 5 | 1 | 1 |  white/blue |
| 6 | 2 | 2 |  orange |
| 7 | 4 | 1 |  white/brown |
| 8 | 4 | 2 |  brown |
| Pin | Pair | Wire | Color |
|---|---|---|---|
| 1 | 2 | 1 | white/orange |
| 2 | 2 | 2 | orange |
| 3 | 3 | 1 | white/green |
| 4 | 1 | 2 | blue |
| 5 | 1 | 1 | white/blue |
| 6 | 3 | 2 | green |
| 7 | 4 | 1 | white/brown |
| 8 | 4 | 2 | brown |
Cable types, connector types and cabling topologies are defined byANSI/TIA-568. Category 5 cable is nearly always terminated with8P8C modular connectors (often referred to incorrectly asRJ45 connectors[14][15][16]). The cable is terminated in either theT568A scheme or theT568B 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 forcomputer networks such asEthernet over twisted pair. The cable standard prescribes performance parameters for frequencies up to100 MHz and is suitable for10BASE-T,100BASE-TX (Fast Ethernet),1000BASE-T (Gigabit Ethernet), and2.5GBASE-T.10BASE-T and100BASE-TX Ethernet connections require two wire pairs. 1000BASE-T and faster Ethernet connections require four wire pairs. Through the use ofpower 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 astelephony andvideo.[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] TheUSOC/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 ofbalanced lines helps preserve a highsignal-to-noise ratio despite interference from both external sources and crosstalk from other pairs.
| Property | Nominal | Tolerance | Unit | ref |
|---|---|---|---|---|
| Characteristic impedance,1–100MHz | 100 | ± 15 | Ω | [24] |
| Characteristicimpedance@ 100 MHz | 100 | ± 5 | Ω | [24] |
| DC loop resistance | ≤ 0.188 | Ω/m | [24] | |
| Propagation speed relative to thespeed of light | 0.64 | [24] | ||
| Propagation delay | 5.30 | ns/m | [24] | |
| Delay skew< 100 MHz | < 0.20 | ns/m | [24] | |
| Capacitance at800 Hz | 52 | pF/m | [24] | |
| Max tensile load, during installation | 100 | N | [24] | |
| Wire diameter (24AWG;0.205 mm2)) | 0.51 | mm | [24] | |
| Operating temperature | −55 to +60 | °C | [24] | |
| MaximumDC operating voltage (PoE uses max 57 V)[25] | 125 | V | [26] |
Outer insulation is typicallypolyvinyl chloride (PVC)[27] orlow smoke zero halogen (LS0H).[citation needed]
| Acronym | Material |
|---|---|
| PE | Polyethylene |
| FP | Foamed polyethylene |
| FEP | Fluorinated ethylene propylene |
| FFEP | Foamed fluorinated ethylene propylene |
| AD/PE | Air dielectric/polyethylene |
| LSZH or LS0H | Low smoke, zerohalogen |
| LSFZH or LSF0H | Low smoke and fume, zero halogen |
Most Category 5 cables can be bent at any radius exceeding approximately four times the outside diameter of the cable.[29][30]
The maximum length for a cable segment is 100 meters (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-conductorunshielded twisted pair (UTP) cables for backbone cabling is required to be no thicker than 22American 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 four pairs are common, Category 5 is not limited to four pairs. Backbone applications involve using up to100 pairs.[37]
The distance per twist is commonly referred to as pitch. Each of the four pairs in a Cat 5 cable has a differing pitch to minimizecrosstalk between the pairs. The pitch of the twisted pairs is not specified in the standard.
 | It has been suggested that this section besplit into a new article titledTwisted pair, because Applies not only Cat 5, but to all communication cabling. (Discuss)(June 2023) |
| Class | Phrase | Description | Standards |
|---|---|---|---|
| LSZH | Communications low-smoke zero halogen | NES‑711, NES‑713, MIL‑C‑24643, UL 1685 | |
| 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. | CSA FT6[39] orNFPA 262 (UL 910) |
| CMR | Communications riser | Insulated with high-density polyolefin and jacketed with low-smoke polyvinyl chloride (PVC). | UL 1666 |
| CMG | Communications general purpose | CSA FT4 | |
| CM | Communications | Insulated 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 |
| CMX | Communications residential | UL 1581, Sec. 1080(VW-1) | |
| CMH | CSA FT1 |
Some cables areUV-rated orUV-stable meaning they can be exposed to outdoorUV radiation without significant degradation.[40]
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 inplenum spaces where PVC is not allowed.[41][self-published source?]
Shielded cables (FTP or STP) are useful for environments where proximity toRF equipment may introduceelectromagnetic interference, and can also be used whereeavesdropping likelihood should be minimized.
The RJ (registered jack) prefix is one of the most widely (and incorrectly) used prefixes in the computer industry; nearly everyone, including people working for cabling companies, is guilty of referring to an eight-position modular jack (sometimes called an 8P8C) as an RJ-45.
The traditional 8-contact connector, which is called Western Plug, 8PMJ (8-position modular jack), 8P8C (8 position 8 conductor), or somewhat incorrectly RJ-45, is used widely in SCS practice.
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.
carry one old fashioned analog telephone signal and one 10/100 Mbps Ethernet signal by the same single network cable.
