Cable and Connector Types

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There are four major types of network cables:

  • Unshielded twisted pair (UTP)

  • Shielded twisted pair (STP)

  • Fiber- optic

  • Coaxial

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Infrared (IR) ports built into many notebook computers can also be used with direct cable connection.


Network cards are designed to interface with one or more types of network cables.

Serial (RS-232) null modem and parallel (LPT) crossover cables can be used with direct cable connection, which is a special type of two-station network included in Windows that uses standard network protocols but does not use network cards.

UTP and STP Cabling

Unshielded twisted pair ( UTP ) cabling is the most common of the major cabling types. The name refers to its physical construction:four twisted pairs of wire surrounded by a flexible jacket.

UTP cable comes in various grades, of which Category 5 is the most common of the standard cabling grades. Category 5 cabling is suitable for use with both standard 10BaseT and Fast Ethernet networking, and can also be used for Gigabit Ethernet networks if tested for compliance.

Shielded twisted pair ( STP ) cabling (Category 4) is designed for use on IBM Token-Ring Networks. STP uses the same RJ-45 connector as UTP, but includes wire mesh for electrical insulation between the wire pairs and the outer jacket. It's stiffer and more durable, but also more expensive and harder to loop through tight spaces than UTP. Type 1 STP cable used by older token-ring adapters has a 9-pin connector.

Table 21.4 lists the various types of UTP and STP cabling in use and what they're best suited for.

Table 21.4. Categories and Uses for UTP and STP Cabling

Category

Network Type(s) Supported

Supported Speeds

Notes

1

Telephone, DSL, Home PNA

Up to 100Mbps (HomePNA)

 

2

LocalTalk

Up to 4Mbps

Obsolete

3

10BaseT Ethernet

Up to 10Mbps

Replace with Category 5 or greater

4

Token ring

Up to 16Mbps

Shielded twisted pair (STP)

5

10BaseT, 100BaseT, 1000BaseT

Up to 1,000Mbps

 

5e

10BaseT, 100BaseT, 1000BaseT

Up to 1,000Mbps

Enhanced version of Category 5

6

10BaseT, 100BaseT, 1000BaseT

Up to 1,000Mbps

Handles higher frequencies than Category 5

7

10BaseT, 100BaseT, 1000BaseT

Up to 1,000Mbps

Uses 12-connector GG45 connector (backward compatible with RJ-45)

Figure 21.8 compares Ethernet cards using UTP, thin coaxial, and thick coaxial cables and connectors to each other.

Figure 21.8. Combo UTP/BNC/AUI Ethernet network cards (left and right) compared with a UTP-only Ethernet card (center) and cables.

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The connector used by Ethernet cards that use UTP is called an RJ-45 connector, and it resembles a larger version of the RJ-11 connector used for telephone cabling. UTP cabling runs between a computer on the network and the hub, which routes signals to other computers (servers or workstations) on the network. It can be purchased in prebuilt form or as bulk cable with connectors, so you can build the cable to the length you need.

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Hubs connect different computers with each other on the network. See "Switches and Hubs," p. 789 , for more information.


To attach UTP cable to a network card or other device, plug it into the connector so that the plastic locking clip snaps into place; the cable and connector will fit together only one way. Squeeze the locking clip toward the RJ45 connector and pull the connector out of the RJ45 jack if you need to remove the cable. Some cables use a snagless connector; squeeze the guard over the locking clip to open the clip to remove the cable.

UTP cable can be purchased in prebuilt assemblies or can be built from bulk cable and connectors.

Fiber Optic

Fiber-optic cabling transmits signals with light rather than with electrical signals, which makes it immune to electrical interference. It is used primarily as a backbone between networks. Fiber-optic cable comes in two major types:

  • Single-mode ” Has a thin core designed to carry a single light ray long distances.

  • Multi-mode ” Has a thicker core than single-mode; carries multiple light rays for short distances.

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When Ethernet is run over fiber-optic cables, the letter F is used in place of T (twisted pair) in the name. For example, 10BaseF is 10Mbps Ethernet running on fiber-optic cable, 100BaseF is 100Mbps Ethernet running on fiber-optic cable, and so on.


Fiber-optic cabling can be purchased prebuilt, but if you need a custom length, it should be built and installed by experienced cable installers because of the expense and risk of damage. Some network adapters built for servers are designed to use fiber-optic cable. Otherwise, media converters are used to interconnect fiber optic to conventional cables on networks.

Coaxial

Coaxial cabling is the oldest type of network cabling; its data wires are surrounded by a wire mesh for insulation. Coaxial cables, which resemble cable TV connections, are not popular for network use today because they must be run from one station directly to another rather than to or from a hub/switch.

Coaxial cabling creates a bus topology; each end of the bus must be terminated , and if any part of the bus fails, the entire network fails.

The oldest Ethernet standard, 10Base5, uses a very thick coaxial cable (RG-8) that is attached to a NIC through a transceiver that uses a so-called "vampire tap" to connect the transceiver to the cable. This type of coaxial cable is also referred to as Thick Ethernet or Thicknet.

Thin Ethernet, also referred to as Thinnet, Cheapernet, or 10Base2 Ethernet was used for low-cost Ethernet networks before the advent of UTP cable. The coaxial cable used with 10Base2 is referred to as RG-58. This type of coaxial cable connects to network cards through a T-connector that bayonet-mounts to the rear of the network card using a BNC connector. The arms of the T are used to connect two cables, each running to another computer in the network.

If the workstation is at the end of a network, a terminating resistor is connected to one arm of the T to indicate the end of the network (refer to Figure 21.8). If a resistor is removed, the network fails; if a station on the network fails, the network fails.

Two other types of coaxial cable are common in cable Internet, satellite Internet, and fixed wireless Internet installations:

  • RG-59 ” Used in older cable TV or satellite TV installations; 75-ohm resistance. Also used by the long-obsolete Arcnet LAN standard.

  • RG-6 ” Uses same connectors as RG-59, but has a larger diameter with superior shielding; used in cable TV/Internet, satellite TV/Internet, and fixed wireless Internet/TV service; 75-ohm resistance.

Plenum and PVC

The outer jacket of UTP, STP, and coaxial cable is usually made of PVC (polyvinyl chloride), a low-cost durable vinyl compound. Unfortunately, PVC creates dense poisonous smoke when burned. If you need to run network cable through suspended ceiling or air vents, you should use more-expensive plenum cable, which produces less smoke and a lower level of toxic chemicals when burned.

Connector Types

Most coaxial cables, including RG-58, RG-59, and RG-6 use a BNC (Bayonet Neill-Concelman) connector. RG-58 uses a T-adapter to connect to a 10Base2 Ethernet adapter. RG-11 (Thicknet) cable is connected to an Ethernet card by means of an external transceiver, which attaches to the AUI port on the rear of older Ethernet network cards. The transceiver attaches to the cable with a so-called "vampire tap."

10BaseT, 100BaseT, and 1000BaseT Ethernet cards using copper wire all use the RJ-45 connector shown in Figure 21.8, as do newer token-ring and all ISDN and cable Internet devices.

DSL devices often use the RJ-11 connector shown in Figure 21.3, as do dial-up modems.

Older token-ring cards use the 9-pin DB-9 Type 1 STP cable; the cable has a male connector and the card has a female connector.

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Absolute Beginners Guide to A+ Certification. Covers the Hardware and Operating Systems Exam
Absolute Beginners Guide to A+ Certification. Covers the Hardware and Operating Systems Exam
ISBN: N/A
EAN: N/A
Year: 2004
Pages: 310

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