3.1 Copper Cables and Connectors

Twisted Pair Facts

Twisted Pair Standards

Twisted pair cables support a wide variety of fast modern network standards. Key points about twisted pair standards are:

• Two copper conductors form a path for an electrical signal with each wire carrying an equal but opposite signal.
• The wires are twisted to reduce crosstalk (the absorbed signals from another pair).
• The conductors are 22- to 24-gauge in thickness and are covered in plastic insulation.
• Pairs are color coded, bundled together, and covered in a plastic jacket or sheath.
• Most cables contain four twisted pairs.
• Cables may contain 25 or 100 pairs when used in larger wiring applications.
• Each pair within a length of cable is given a different number of twists to further reduce the effects of crosstalk.

Twisted Pair Advantages

Advantages of twisted pair cabling include:

• Flexibility - You can install twisted pair cabling around tight corners and places where other types of network cable cannot go without being damaged.
• Cost - Twisted pair cabling is less expensive than other types of network cabling.
• Ease of use - Twisted pair cabling is easy to work with. It's much easier to install compared to other types of network cabling.
• Support for newer protocols - newer, faster network protocols and standards have been designed to run on twisted pair cabling.

Twisted Pair Disadvantages

Disadvantages of twisted pair cabling include that it is:

• Susceptible to interference - The sheath around twisted pair cable is relatively thin, making it susceptible to EMI.
• Susceptible to eavesdropping - With the right equipment, anyone can pick up signals emanating from the wire.

Twisted Pair Abbreviations

There are two common abbreviations for twisted pair cables.

• Unshielded twisted pair (UTP). UTP cables are easy to work with and less expensive than shielded cables.
• Shielded twisted pair (STP):
  • Shielding is electrically conductive foil or braided material that is wrapped around pairs of wires, around the overall cable, or both.
  • Shielding helps to minimize crosstalk.
  • The main purpose of shielding is to minimize the effects of EMI from external sources, such as fluorescent light ballasts.
  • The shielding can be used as a ground. However, most shielded cables have a special grounding wire called a drain wire.

Plenum and Riser

Specially manufactured twisted pair cables are used in plenum and riser spaces. Key points are:

• A plenum space is a part of a building that provides a pathway for the airflow needed by heating and air conditioning systems, such as above a dropped ceiling or below a raised floor.
• Plenum rated cables use insulation that is fire resistant and non-toxic when burned.
• You must use plenum rated cables in plenum spaces.
• Riser rated cables are designed for installations that run between floors.
• Riser requirements are not as strict as plenum requirements.
  • You can use plenum rated cables in riser spaces.
  • You should never use riser rated cables in plenum spaces.

Solid vs. Stranded

Twisted pair cables can be solid or stranded. Be aware that:

• Solid wires conduct electrical signals better, but are prone to break when they are repeatedly bent.
• Stranded cables are more flexible, but don't carry signals as well.
• You should use solid cables in permanent and semi-permanent installations.
• You should use stranded cables for patch cords and frequently moved cables.

UTP Cable Types

Type	Connector	Description
Phone cable	RJ11	A phone cable is used to connect a PC to a phone jack in a wall outlet to establish a dial-up internet connection. It is also used to connect a DSL modem to a telephone network. It has two pairs of twisted cable (a total of 4 wires).
Cat 5	RJ45	Cat 5 supports 100-Mb Ethernet (100BASE-TX) and ATM networking. Cat 5 specifications also support gigabit (1000 Mb) Ethernet.
Cat 5e	RJ45	Cat 5e is similar to Cat 5 but provides better EMI protection. It supports 100-Mb (100BASE-T) and gigabit (1000BASE-T) Ethernet.
Cat 6	RJ45	Cat 6 supports 10-Gbps Ethernet (10GBASE-T) and high-bandwidth broadband communications. In most cases, Cat 6 cables include a solid plastic core that keeps the twisted pairs separate and prevents the cable from being bent too tightly.
Cat 6a	RJ45	Cat 6a is designed to provide better protection against EMI and crosstalk than Cat 6 cabling. Cat 6a provides better performance than Cat 6, especially when used with 10-Gbps Ethernet (10GBASE-T).
Cat 7	GG45/TERA	The Cat 7 standard was ratified years before the Cat 6a standard to support 10-Gbps Ethernet (10GBASE-T). It requires shielding on each twisted pair and the cable as a whole. It also specifies the GG45 or TERA connectors.
Cat 8	RJ45	This is the fastest Ethernet cable with data transfer speed of up to 40 Gb and bandwidth support of up to 2 GHz. Cat8 uses shielded foiled twisted pair construction that includes shielding around each pair of wires within the cable to reduce near-end crosstalk.

It also uses braiding around the group of pairs to minimize electromagnetic interference in crowded network installations. |

You can substitute each type of UTP cable for any category below it, but never for a category above. For example:

• You can substitute Cat 6 for a standard requiring Cat 5e.
• You can't use Cat 5 in a situation where Cat 6 is required.
• The exception is Cat 7 cabling, and then only when Cat 7 is terminated with TERA connectors.

Connector Types

Connector	Description
RJ11

| The RJ11 connector:

• Has four connectors.
• Supports up to two pairs of wires.
• Uses a locking tab to keep the connector secure in an outlet.
• Is used primarily for telephone wiring. | | RJ45

| The RJ45 connector:

• Has eight connectors.
• Supports up to four pairs of wires.
• Uses a locking tab to keep the connector secure in an outlet.
• Is used for Ethernet and some Token Ring connections.

The RJ48c connector type is almost identical to RJ45. It uses the same connector as an RJ45, but it is wired differently. It is used for specific WAN connections, such as a T1 line. | | GG45

| The GG45 connector:

• Has eight connectors.
• Supports four pairs of wires.
• Is backwards compatible with RJ45.
• Has four additional conductors in the corners of the connector that duplicate and replace the four inner pins on the RJ45. | | TERA

| The TERA connector:

• Has eight connectors.
• Supports four pairs of wires.
• Is incompatible with RJ45 and GG45.
• Does not require special tools to install. |

Coaxial Cable Facts

Coaxial Cable Components

Coaxial cable has the following components:

• Two concentric metallic conductors.
  • The inner conductor is a solid wire made of copper or copper-coated tin.
  • The outer mesh conductor (shield) is made of aluminum or tin-coated copper.
• A PVC plastic insulator that surrounds the inner conductor and insulates the signal from the mesh conductor.
• A PVC plastic cable sheath (jacket) that surrounds and protects the wire.

Coaxial Cable Advantages and Disadvantages

Advantages	Disadvantages
Advantages of coaxial cable include:

• Highly resistant to electromagnetic interference (EMI).
• Highly resistant to physical damage. | Disadvantages of coaxial cable include:
• More expensive than UTP.
• Inflexible construction (more difficult to install).
• Not supported by newer networking standards. |

Coaxial Cable Grades

Grade	Uses	Resistance Rating
RG-58	10Base2 Ethernet networking (also called thinnet)	50 ohms
RG-6	Cable TV, satellite TV, and cable networking	75 ohms

Coaxial Cable Connector

Coaxial cable uses the F-type connector. The F-type connector is:

• Twisted onto the cable or installed using a compression tool.
• Used to create cable and satellite TV connections.
• Used to connect a cable modem to a broadband cable connection.

Questions/Answers

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