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Twisted-pair cables - categories, shielding, applications
Twisted-pair cables are used to transmit signals in telecommunication systems and computer networks. The most popular twisted-pair cables are composed of four pairs of twisted insulated copper wires. The twisting strongly reduces the influence of external electromagnetic interference and mutual interference between the pairs, called crosstalk. Currently, the cables are mainly used in telephony and Ethernet networks.
This article presents types of twisted-pair cables and their classification based on category, structure, application, transmission parameters.
Categories/classes of twisted-pair cables
Categories/classes of twisted pair cables enable users to select proper cables for applications in different networks, and ensure backward compatibility with existing solutions. The requirements for specific categories or classes of structured cabling (including compatibility issues) are defined by the Telecommunications Industry Association (TIA) and the International Organization for Standardization (ISO). The EIA/TIA standard and the European standard EN50173 define several groups of copper cables with different capabilities of data transmission.
  • Category 1 (class A by EN 50173)
    • Telephone voice services with band up to 100 kHz.
  • Category 2 (class B by EN 50173)
    • Voice services and older terminal systems with band up to 1 MHz.
  • Category 3 (class C by EN 50173)
    • Telephone services with band up to 16 MHz.
  • Category 5/5e (class D by EN 50173))
    • The category of computer twisted pair cable most often used in local networks, including applications requiring frequency band up to 100 MHz (FastEthernet 100Base-TX, GigabitEthernet 1000Base-T).
CAT 5e UTP Cable: NETSET U/UTP 5e [1m], indoor
Cat 5e UTP Cable: NETSET U/UTP 5e <br />(outdoor - gel-filled, black) [1m]
CAT 5e UTP cable for indoor applications
NETSET U/UTP 5e E1408
CAT 5e UTP cable for outdoor applications
NETSET U/UTP 5e (gel-filled, black) E1410
Cat 5e UTP Cable: NETSET U/UTP PE (outdoor) [1m]
CAT 5e Shielded Cable: NETSET F/UTP 5e [1m], indoor
Cat5e Shielded Cable: NETSET BOX F/UTP 5e [1m], outdoor
Cat 5e UTP Cable NETSET U/UTP
(PE - outdoor) E1412
CAT 5e Shielded Cable NETSET F/UTP 5e
(indoor) E1515
Cat5e Shielded Cable NETSET BOX F/UTP 5e
(outdoor) E1517
  • Category 6 (class E by EN 50173)
    • Applications requiring frequency band up to 250 MHz, data transfer rates up to 1 Gbps.
CAT 6 Cable: NETSET BOX U/UTP 6 (indoor) [1m]
CAT 6 Cable NETSET U/UTP 6 (indoor) E1608
  • Category 6A (class EA by EN 50173)
    • Applications requiring frequency band up to 500 MHz. Ideal for multimedia transmissions; U/FTP, F/FTP versions.
CAT 6A U/FTP Shielded Cable: NETSET U/FTP 6A [500m], indoor
CAT 6A U/FTP Shielded Cable NETSET U/FTP 6A (indoor) E1616_500
  • Category 7 (class F by EN 50173)
    • Category 7 cables allow for applications requiring frequency band up to 600 MHz. Compared with the lower categories, each pair of the S/FTP cables is individually screened and all the pairs are wrapped up in another shielding layer. The connectors for the cables are shielded as well.
  • Category 7A (class FA by EN 50173)
    • Applications requiring frequency band up to 1000 MHz. Allows for data transfer rates up to 100 Gbps over distances up to 15 m or 40 Gbps over distances up to 100 m.
Shielding
The use of electrical shielding/screening ensures that the signals transmitted via the pairs are less susceptible to ambient interference and, analogically, they create lower levels of external electromagnetic interference. However, the use of shielded cables requires knowledge of the principles of proper shielding and their practical implementation, including equipotential connections and grounding infrastructure in the building(s). The basic principle is to properly ground the screen at both ends of the cables.
Kinds of twisted-pair cables:
  • U/UTP – unshielded
1. White-blue/blue pair of wires
2. White-brown/brown pair of wires
3. White-orange/orange pair of wires
4. White-green/green pair of wires
5. Jacket/sheath
6. Rip-cord
7. Core conductor (applies to all wires)

  • F/UTP – foil-shielded cable with unshielded twisted pairs
1. White-blue/blue pair of wires
2. White-brown/brown pair of wires
3. White-orange/orange pair of wires
4. White-green/green pair of wires
5. Jacket/sheath
6. Rip-cord
7. Core conductor (applies to all wires)
8. Drain wire
9. Cable shield

  • U/FTP – cable with individually foil-shielded twisted pairs
1. White-blue/blue pair of wires
2. White-brown/brown pair of wires
3. White-orange/orange pair of wires
4. White-green/green pair of wires
5. Jacket/sheath
6. Rip-cord
7. Core conductor (applies to all wires)
8. Drain wire
9. Pair shield (applies to all pairs)
  • F/FTP – foil-shielded cable with individually foil-shielded twisted pairs
1. White-blue/blue pair of wires
2. White-brown/brown pair of wires
3. White-orange/orange pair of wires
4. White-green/green pair of wires
5. Jacket/sheath
6. Rip-cord
7. Core conductor (applies to all wires)
8. Drain wire
9. Cable shield
10. Pair shield (applies to all pairs)


  • SF/FTP – braid-and-foil shielded cable with individually foil-shielded twisted pairs
1. White-blue/blue pair of wires
2. White-brown/brown pair of wires
3. White-orange/orange pair of wires
4. White-green/green pair of wires
5. Jacket/sheath
6. Rip-cord
7. Core conductor (applies to all wires)
8. Drain wire
9. Foil cable shield
10. Pair shield (applies to all pairs)
11. Braid screen

  • S/FTP – braid-and-foil shielded cable with individually foil-shielded twisted pairs
1. White-blue/blue pair of wires
2. White-brown/brown pair of wires
3. White-orange/orange pair of wires
4. White-green/green pair of wires
5. Jacket/sheath
6. Rip-cord
7. Core conductor (applies to all wires)
8. Drain wire
10. Pair shield (applies to all pairs)
11. Braid screen

  • SF/UTP – braid-and-foil shielded cable with unshielded twisted pairs
1. White-blue/blue pair of wires
2. White-brown/brown pair of wires
3. White-orange/orange pair of wires
4. White-green/green pair of wires
5. Jacket/sheath
6. Rip-cord
7. Core conductor (applies to all wires)
8. Drain wire
9. Foil cable shield
11. Braid screen
Applications
There are two distinct groups of cables, for outdoor and indoor applications.
  • Outdoor
    • The most important feature of outdoor cables is their resistance to difficult and changeable environment conditions. The main influence ion this feature has the kind and quality of the material used for the jacket. There are available cables with PVC and polyethylene (PE) jacket. PE is harder than PVC, has a higher mechanical strength and chemical resistance, and makes a better barrier against gases.
  • Indoor
    • When using cables inside buildings, a special attention should be paid to the requirements concerning reaction of the wiring to fire. Dedicatedl types of insulation, for example LSOH or LSZH (Low Smoke Zero Halogen) polymers, are safe when exposed to fire. In comparison with PVC, PE does not produce harmful and toxic substances (halogens), and also does not generate such large amounts of smoke. The use of cables in LSZH coatings is very often a requirement of fire regulations in large buildings.
Data transfer rates
The EIA/TIA standard defines several groups of twisted-par cables taking into account their suitability for transmission of information (categories). Most new cable installations are based on CAT 5e cabling. The information on electrical / transmission parameters of the categories determines their maximum data transfer rates.
  • Category 3 (class C by EN 50173)
    • 4 Mb/s - (10BaseT, RS 232)
  • Category 5 (class D by EN 50173)
    • 1 Gb/s - (1000BaseT, ATM 155)
  • Category 6 (class E by EN 50173)
    • 1 Gb/s - (1000BaseT)
    • 10 Gb/s - (10GBASE-T up to 55m)
  • Category 6A (class EA by EN 50173)
    • 10 Gb/s - (10GBASE-T)
Fire performance of cables
Until now, the conductors and cables were treated exclusively as electrical products subject to product safety regulations under the Low Voltage Directive (LVD) and were subject to CE marking by the manufacturer. The new rules established by EN50575 impose on the manufacturers (also importers and distributors) the obligation to commission relevant tests to notified certification bodies/laboratories in order to obtain certificates confirming the fire resistance classes of their products and to issue Declarations of Performance (DoP) with the relevant Euroclasses. The Euroclass of a construction product (including power, control and communication cables) allows for its classification in terms of reaction to fire according to the same rules and criteria across Europe. The markings of the fire classification can already be found on the labels of many construction products and will soon be required for all such products. More info here.
Euroclass
Test methods
Additional classification
Examples of products
 AcaEN ISO 1716 halogen-free cables
 B1ca EN 50399
EN 60332-1-2
smoke production (s1, s2),
flaming droplets/particles (d1,d2)  
and acidity (a1)
halogen-free cables
 B2ca EN 50399
EN 60332-1-2
hard PVC and halogen-free cables
 Cca EN 50399
EN 60332-1-2
halogen-free cables
Dca EN 50399
EN 60332-1-2 
high-quality PVC cables
 EcaEN 60332-1-2  no performance determined (NPD)
PVC cables
 Fca

Not fulfilling requirements
for
Eca

 no performance determined (NPD) PE and PVC cables

Cable classification scheme according to EN50575 standard
CodeNameDoP
PL
DoP
EN
CategoryReaction to fire
E1408NETSET U/UTP5e  Eca
E1410NETSET U/UTP PE+ żel 5e  Fca
E1412NETSET U/UTP PE 5e Fca
E1515NETSET F/UTP 5e Eca
E1517NETSET F/UTP PE 5e Fca
E1608NETSET U/UTP  Eca
E1616NETSET U/FTP6A Eca

List of Declarations of Performance of coaxial cables compliant with CPR
 
George Popescu
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