Category 5 (CAT5) Cabling

Category 5 (CAT5) Cabling

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 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 (AWG) copper wires within the cables.

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 (“GigE”) 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 100 m maximum). Cat 5e cable performance characteristics and test methods are defined in TIA/EIA-568-B.2-2001.

Manufacture of Solid Core Cable

Copper Rod Breakdown The first step in low voltage cable production is copper rod breakdown. Copper is sent to the factory in 5,000 lb coils. These copper coils are continuously drawn through diamond dies that drastically reduce the diameter of the copper to 10 or 12 gauge. Lubrication is used during this process to reduce the amount of friction and heat on the copper cable. Once completed, the copper is stacked in vertical coils, called Stem Packs. These stem packs are then transferred to another drawing operation that further reduces the gauge of the copper. During this stage, the copper is also charged with an electrical current. This anneals the copper, which is a softening process. Once annealed and cooled off, the copper runs through a laser measurement system, to verify it is within manufacturing specifications.

Copper Insulation Process The copper insulation process is continually monitored and controlled up to +/- .0001″. Once the copper is insulated, it runs through a water cooling trough, allowing the wire jacket to properly harden.

Copper Twisting Twisting helps reduce crosstalk between the individual pairs of wire. Some Cat6 premise cables include a center spline, or wire separator, to further reduce crosstalk and increase performance. Copper twisting is accomplished by running each individual wire through multiple faceplates. This helps control pair position. Once twisted, we have what’s called a Cable Unit.

Jacketing The cable unit then goes through the jacketing process. This step varies, depending on the type of cable being manufactured. OSP cable typically uses a black polyethylene or UV rated Polyvinyl chloride (PVC). For Cat3, Cat5e and Cat6 Premise cable, varying grades of PVC are used, depending on flame safety rating requirements. This steps starts off with molten plastic being extruded at high pressure and formed around the moving cable core. Shielding, ripcords, armoring and water blocking compound may also be applied at this step. Cables that require dual shielding or double armor will need to repeat this process. Once completed, the cable passed through a long cooling bath, then through a laser micrometer to verify the final diameter.

Printing Printing is done just before the cable is put in its final packaging. For OSP cable, a hot foil printing process is used, that leaves an indented print in the cable jacket. For Premise cable, a high speed ink jet printer is used. Some cable manufacturers print footage marking from 1000–0 ft, making it very easy to determine how much cable is left in the box, or for measuring out cable runs. Other manufacturers use a six digit footage mark, making the process a little harder.

Coiling The completed cable is then wound onto a reel or coil. the coiling process requires very precise tension controls to ensure the cable won’t tangle when being pulled out of the box.

Final Testing Once the cable is printed and coiled, it goes through one last set of tests. The manufacturer will test it against a large set of mechanical and electrical performance specifications. Once tested, the cable is ready for shipment.

Solid core Cable vs Stranded Cable

Solid core cable is cheaper and is used for long permanently installed runs and care should be taken to avoid bending the conductors as the conductors may crack. The vibration from even small movements, such as from a fan, may cause cracking of solid core.
Stranded cable is used for fly leads at patch panel and for connection to movable or vibrating devices, as it resists cracking of the conductors. Stranded is more expensive and therefore commonly used for short runs.

There is a different type of crimp connector for solid core than for stranded . Use of the wrong type connector may lead to unreliable cabling.

Low-end cable problem

The Communications Cable and Connectivity Association, Inc. (CCCA) in 2008 cautioned that many low-end communications cable products could present a significant fire risk. In response to concerns from the industry, the CCCA commissioned an independent laboratory to analyze whether nine randomly selected low end samples of these products met U.S. minimum requirements for performance and safety. Test results showed that none of the samples fully met all of the minimum requirements and eight of the nine samples failed to meet the National Fire Protection Association (NFPA) minimum code requirements for low flame spread and/or smoke safety requirements for installation in commercial buildings, schools and multi-tenant residences. Many of the samples failed the flame spread and smoke tests catastrophically. Because of the seriousness of these safety concerns, the CCCA plans to work in cooperation with the major leading independent telecommunications industry testing agencies to establish a new product certification program. Although details of the proposed program have not yet been established, a key component will be independent laboratory testing of structured cabling products that have been procured from point–of-sale locations

Conductors required

10BASE-T (IEEE) and 100BASE-TX (IEEE) Ethernet connections require two cable pairs. 1000BASE-T (IEEE) and 1000BASE-TX (TIA/EIA-854, requiring category 6 cabling, unimplemented) Ethernet connections require four cable pairs. Four pair cable is by far most commonly available type.

Bending radius

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

Electrical characteristics for Cat.5e UTP

PropertyNominal ValueToleranceUnitref
Characteristic impedance @ 100 MHz100± 15Ω[11]
Nominal characteristic impedance @ 100 MHz100± 5Ω[11]
DC-Loop resistance≤ 0.188Ω/m[11]
Propagation speed0.64c[11]
Propagation delay4.80-5.30ns/m[11]
Delay skew < 100 MHz<0.20ns/m[11]
Capacitance at 800 Hz52pF/m[11]
Inductance525nH/m[12]
Cutoff frequency50323Hz[12]
Max tensile load, during installation100N[11]
Wire sizeAWG-24(0.205 mm² )[11][13]
Insulation thickness0.245mm[11]
Maximum current per conductor0.577A[13]
Temperature operating-55 to +60°C[11]

Dielectric

Example materials used as dielectric in the cable:

AcronymMaterial
PEPolyethylene
FPFoamed polyethylene
FEPTeflon / Fluorinated Ethylene Propylene
FFEPFoamed Teflon / Fluorinated Ethylene Propylene
AD/PEAir dielectric / Polyethylene

 

Individual twist lengths

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

Pair color[cm] per turnTurns per [m]
Green1.5365.2
Blue1.5464.8
Orange1.7856.2
Brown1.9451.7

 

Environmental ratings

US & Canada Fire certifications:

ClassAcronymStandards
CMPPlenumCSA FT7 [15] or NFPA 262 [15](UL 910)
CMRRiserUL 1666
CMGGeneral purposeCSA FT4
CMUL 1685 (UL 1581, Sec. 1160) Vertical-Tray
CMXResidentialUL 1581, Sec. 1080 (VW-1)
CMHCSA FT1

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

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.

Any cable which 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 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. 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.

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.

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