Category 5 cable

Category 5 patch cable in TIA/EIA-568-B wiring

Category 5 cable, is a twisted pair high signal integrity cable type often referred to as Cat5. Most cables are unshielded relying on the twisted pair design for noise rejection, and 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 Category 5 has been superseded by the Category 5e specification structured cabling for computer networks such as Ethernet, and is also used to carry many other signals such as basic voice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).

Usage and wiring methods

8P8C modular plug pin positioning

TIA/EIA-568-B.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 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

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.

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TURN YOUR SWAG ON

The Communications Cable and Connectivity Association, Inc.(CCCA) cautioned that many low end communications cable products could present 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..

Cat 5e “350 MHz” The Debacle

The 350 MHz term started a couple of years before the arrival of Category 6 cable by the Belden Electronics Division and promised better performance. Although the performance of this new 350 MHz cable was slightly better it was an easy way to sell the consumer on future proofing their needs while charging around 15% more and leading to a higher margin on the 350 MHz cable than the standard 5e cable. Soon after many other manufactures also offered a 350 MHz cable and followed the trend of an easy way to add to a higher margin. Some low-end cable manufacturers have the term “tested to 350 MHz,” printed on the jacket as a way to appear to the consumer that they are receiving a higher end of 5e cable, but the cable was only “tested to 350 MHz” and no promise of a performance guarantee is ever mentioned.

As the 350 cable and term gained momentum many manufacturers began offering a 400 MHz 5e cable a 550 MHz 5e cable and so on. This led to the consumer and communications contractor assuming and leaving them confused that the higher a MHz rating meant for a better performing cable. The arrival of the Category 6 cable standard which specified a delivered performance at 250 MHz left many people confused.

EIA Electronic Industries Alliance / TIA Telecommunications Industry Association only recognize the Category 5e standard TIA/EIA-568-B.2-2001 as guaranteeing performance of Attenuation, NEXT, Power-sum NEXT, ACR, Power-sum ACR, ELFEXT, Power-sum ELFEXT, Return loss, Propagation delay and delay skew at 100 MHz. No standard is issued for 350 MHz cable and upon review of manufacturer spec sheets such as General Cable, Superior Essex, and Berktek show us different performance numbers for 350 MHz. With no standard for 350 MHz cable, promised performance, if any, will vary from manufacturer to manufacturer and leave the consumer and contractor to continue to be confused.

Conductors Required

10BASE-TX and 100BASE-TX ethernet connections require two cable pairs. 1000BASE-TX 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

Property	Nominal Value	Tolerance	Unit	ref
Characteristic impedance @ 100 MHz	100	± 15	Ω
Nominal characteristic impedance @ 100 MHz	100	± 5	Ω
DC-Loop resistance	≤ 0.188		Ω/m
Propagation speed	0.64		c
Propagation delay	4.80-5.30		ns/m
Delay skew < 100 MHz	<0.20		ns/m
Capacitance at 800 Hz	52		pF/m
Inductance	525		nH/m
Cutoff frequency	50323		Hz
Max tensile load, during installation	100		N
Wire size	AWG-24 (0.205 mm² )
Insulation thickness	0.245		mm
Maximum current per conductor	0.577		A
Temperature operating	-55 to +60		°C

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

Individual twist lengths

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

	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:

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)
CMH		CSA 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.

See also

• Category 6 cable
• Category 7 cable
• American wire gauge (AWG)
• Ethernet over twisted pair (10/100/1000Base-T)
• Power over Ethernet (PoE)

Further reading

• cat5ecables.co.uk - CAT5e cable information, colour codes and pinouts, learn how to make patch leads
• ikestechblog.com - How to make your own Cat5 cable
• unioncopper.com - Cable exploded view and which materials used
• computercablestore.com - How to make Cat5e patch cables - Detailed step by step