Category 5 cable

Category 5 cable (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. It is also used to carry other signals such as telephony and video. The cable is commonly connected using punch down blocks and modular connectors. Most Category 5 cables are unshielded, relying on the twisted pair design and differential signaling for noise rejection. Category 5 has been superseded by the Category 5e (enhanced) specification.

TIA/EIA-568-A.1-2001 T568A Wiring 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

TIA/EIA-568-B.1-2001 T568B Wiring[1] 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

USOC/RJ61 Wiring Pin Pair Wire Color 1 4 tip white/brown 2 3 tip white/green 3 2 tip white/orange 4 1 ring blue 5 1 tip white/blue 6 2 ring orange 7 3 ring green 8 4 ring brown Partially stripped cable showing the twisted pairs.

A Cat 5e Wall outlet showing the two wiring schemes: A for T568A, B for T568B.

Contents 1 Cable standard 1.1 Conductors required 1.2 Bending radius 1.3 Maximum cable segment length 2 Characteristics 2.1 Insulation 2.2 Individual twist lengths 2.3 Environmental ratings 3 See also 4 References

Cable standard

The specification for Category 5 cable was defined in ANSI/TIA/EIA-568-A, with clarification in TSB-95.^{[citation needed]} These documents specified performance characteristics and test requirements for frequencies of up to 100 MHz. Cable types, connector types and cabling topologies are defined by TIA/EIA-568-B. 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. Nearly always, 8P8C modular connectors, often referred to as RJ45, are used for connecting category 5 cable. The USOC/RJ-61 standard is used in multi-line telephone connections.
Each of the four pairs in a Cat 5 cable has differing precise number of twists per metre 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.^[2] This use of balanced lines helps preserve a high signal-to-noise ratio despite interference from both external sources and crosstalk from other pairs. Category 5 cabling is most commonly used for faster Ethernet networks, such as 100BASE-TX and 1000BASE-T.
The cable is available 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 (IDCs).^{[clarification needed]} The solid form is less expensive^{[citation needed]} and makes reliable connections into insulation displacement connectors, but makes unreliable connections in insulation piercing connectors.^{[clarification needed]} 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. The specific category of cable in use can be identified by the printing on the side of the cable.^[3]

Conductors required

10BASE-T and 100BASE-TX Ethernet connections require two cable pairs. 1000BASE-T Ethernet connections require four cable pairs. Cat 5 and Cat 5e cables typically use 24 - 26 AWG wire. Category 6 cable tends to have slightly more copper in each cable, with standard gauges of 22 - 24 AWG.^{[citation needed]}

Bending radius

Most Category 5 cables can be bent at any radius exceeding approximately four times the diameter of the cable.^[4]

Maximum cable segment length

According to the ANSI/TIA/EIA standard for category 5e copper cable (TIA/EIA 568-5-A^[5]), the maximum length for a cable segment is 100 meters (328 feet). If longer runs are required, the use of active hardware such as a repeater, or a switch, is necessary.^[6][7] The specifications for 10BASE-T networking specify a 100 metre length between active devices.^[8] This allows for 90 metres of fixed cabling, two connectors and two patch leads of 5 metres, one at each end.

Characteristics

Electrical characteristics for Cat 5e UTP

Property	Nominal Value	Tolerance	Unit	ref
Characteristic impedance @ 100 MHz	100	± 15	Ω	[9]
Nominal characteristic impedance @ 100 MHz	100	± 5	Ω	[9]
DC-Loop resistance	≤ 0.188		Ω/m	[9]
Propagation speed	0.64		c	[9]
Propagation delay	4.80-5.30		ns/m	[9]
Delay skew < 100 MHz	< 0.20		ns/m	[9]
Capacitance at 800 Hz	52		pF/m	[9]
Inductance	525		nH/m	[10]
Corner frequency	≤ 57		kHz	[10]
Max tensile load, during installation	100		N	[9]
Wire diameter	AWG-24 (0.51054 mm  ; 0.205 mm² )			[9][11]
Insulation thickness	0.245		mm	[9]
Maximum current per conductor	0.577		A	[11]
Temperature operating	-55 to +60		°C	[9]
Maximum operating voltage (PoE uses max 57 V DC)[12]	125		V DC	[13]

Insulation

Example materials used as insulation in the cable^[14]

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

Individual twist lengths

By altering the length of each twist, crosstalk is reduced, without affecting the characteristic impedance.^{[10][dubious – discuss]} The distance per twist is commonly referred to as pitch.

	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

Environmental ratings

US & Canada fire certifications^[15][16]

Class	Phrase	Standards
CMP	Communications Plenum	CSA FT6[17] or NFPA 262[18] (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)
CMH		CSA FT1

CMR (Communications Riser), insulated with high-density polyolefin and jacketed with low-smoke polyvinyl chloride (PVC) can be replaced by a 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.^[15]
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.^[19]
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.^[20] 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 affects legal requirements for a fire sprinkler system. That is if a plenum-rated cable is used, sprinkler requirement may be eliminated.^[21]
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.