Category 5 cable

From Wikipedia, the free encyclopedia

Jump to: navigation, search
Category 5 patch cable in TIA/EIA-568-B wiring

Category 5 cable, is a twisted pair (4 pairs) high signal integrity cable type often referred to as "Cat5". Many such cables are unshielded but some are shielded. Category 5 has been superseded by the Category 5e specification structured cabling for computer networks such as Ethernet, and is also used to carry many other signals such as basic voice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).


[edit] Usage and wiring methods

8P8C modular plug pin positioning
TIA/EIA-568-A.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
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
Image of partially stripped cable showing the twisted pairs.
Image of a Cat 5E Wall outlet showing the two wiring schemes: A for T568A, B for T568B.

[edit] Category 5

The 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 cables.

[edit] 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 as 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 100 m (328 ft) 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, this comes to a total of the previous mentioned 100m maximum). Cat 5e cable performance characteristics and test methods are defined in TIA/EIA-568-B.2-2001.

[edit] 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. Outer insulation is typically PVC or LSOH.

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 specific category of cable in use can be identified by the printing on the side of the cable.[1]

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. 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 could cause signal degradation. The article Ethernet over twisted pair describes how the cable is used for Ethernet, including special "cross over" cables.

[edit] Bending radius

Most Cat.5 cables can be bent at a radius approximately 4 times the diameter of the cable.[2]

[edit] Electrical characteristics for Cat.5e UTP

Property Nominal Value Tolerance Unit ref
Characteristic impedance @ 100 MHz 100 ± 15 Ω [3]
Nominal characteristic impedance @ 100 MHz 100 ± 5 Ω [3]
DC-Loop resistance ≤ 0.188 Ω/m [3]
Velocity ratio 0.64 c [3]
Propagation delay 4.80-5.30 ns/m [3]
Delay skew < 100 MHz <0.20 ns/m [3]
Capacitance at 800 Hz 52 pF/m [3]
Inductance 525 nH/m [4]
Cutoff frequency 50323 Hz [4]
Max tensile load, during installation 100 N [3]
Wire size AWG-24 (0.5105 mm² ) [3][5]
Maximum current per conductor 0.577 A [5]
Temperature operating -55 to +60 °C [3]

[edit] Dielectric

Example materials used as dielectric in the cable:

Acronym Material
PE Polyethylene
FP Foamed polyethylene
FEP Teflon / Fluorinated Ethylene Propylene
FFEP Foamed Teflon / Fluorinated Ethylene Propylene
AD/PE Air dielectric / Polyethylene


[edit] Individual twist lengths

By altering the length of each twist, crosstalk is reduced, without affecting the impedance.[4]

Pair color [cm] per turn Turns per [m]
Green 1.53 65.2
Blue 1.54 64.8
Orange 1.78 56.2
brown 1.94 51.7


[edit] Environmental ratings

Fire certifications:

Class Acronym Standards
CMP Plenum CSA FT7 or NFPA 262 (UL 910)
CMR Riser UL 1666
CMG General purpose CSA FT4
CM UL 1685 (UL 1581, Sec. 1160) Vertical-Tray
CMX Residential UL 1581, Sec. 1080 (VW-1)


Where CMR can be replaced by a CMP and so on, due better rating. CM stands for Communications Cable.[7]

Some cables are "UV rated" meaning they can be exposed to outdoor UV radiation without significant destruction. The materials used for the mantle are usually PVC.[9]

Some cables are suitable for "direct burial", but this usually requires that the cable is 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 which may channel water into sensitive indoor equipment.[10] This can often be solved by adding a drip-loop at the bottom of the run of cable.

Plenum rated cables are slower to burn and produce less smoke than cables using a mantle of materials like PVC. This also affect legal requirements for a fire sprinkler system. That is if a plenum rated cable is used, sprinkler requirement may be eliminated.[11]

Shielded cables (FTP/STP) are useful for environments where proximity to power cables, RF equipment, or high power equipment may introduce crosstalk, and can also be used where interference with radio receivers or where eavesdropping likelihood should be minimised.

[edit] References

  1. ^ Ethernet Cable Identification and Use
  2. ^ "Selecting coax and twisted-pair cable - Electronic Products".  081216
  3. ^ a b c d e f g h i j "SuperCat OUTDOOR CAT 5e U/UTP".  080319
  4. ^ a b c d "Transmission Line Zo".  090113
  5. ^ a b "American Wire Gauge table and AWG Electrical Current Load Limits".  081220
  6. ^ "UL® Listed / ISO 9001 Compliant".  090127
  7. ^ a b "CSA Flame Test Ratings".  090126
  8. ^ "22Technical Information" (PDF). [dead link] 090126
  9. ^ "CAT5e CMR/CMX mean it's uv rated ? -".,16168746.  090126
  10. ^ "A dumb mistake a green WISP operator once made. -".  090126
  11. ^ "What are the differences between PVC, riser and plenum rated cables? - Ask or Answer Questions on Computers & Technology, Ask & Read old Answers on Computers & Technology - ibibo sawaal".  090126

[edit] See also

[edit] Further reading

Personal tools