2.2 Coaxial Cable

Coaxial Cable

In early networks coaxial cable was the cable of choice because it was relatively inexpensive, reliable and robust. It consists of:

  • A central conductor
  • An insulator
  • A braided metallic shielding
  • An outer jacket

The core of a coaxial cable carries the electronic signals and the braided metallic shielding is used to protect the signal from external noise and crosstalk that could cause interference and possibly corrupt the data. Due to this protection, coaxial cable is more resistant to interference and attenuation than twisted pair cabling.

Types of Coaxial Cable

There are two types of coaxial cable:

  • Thinnet cable (10Base2)
  • Thicknet cable (10Base5)

Thinnet (10Base2)

Thinnet coaxial cable is connected using special connectors and requires to be terminated at each end using a 50ohm resistor.

10Base2 stands for:

  • Data Transmission Rate of 10Mbps, i.e. 10
  • Uses baseband transmission, i.e. Base
  • Used in Ethernet networks it has a maximum cable length of 185 metres, i.e. the 2 for approximately 200 metres

Thinnet Connections

Thinnet uses a component, known as a BNC connector, to make the connections between the cable and the computers. There are several important components in the BNC family that include:

  • The BNC cable: The BNC cable connector is either soldered or crimped to the end of a cable
  • The BNC T connector: This connector joins the network interface card (NIC) in the computer to the network cable
  • The BNC barrel: This connector is used to join two lengths of thinnet cable to make one longer length
  • The BNC terminator: A BNC terminator closes each end of the bus cable to absorb stray signals

Note: There are different interpretations about what BNC stands for. Two of the most common are British Naval Connector and Bayonet Neill Concelman.

BNC Components

The BNC components are:

  • T Piece Connector
  • Terminator
  • Barrel Connector
  • Female Connector

Thicknet (10Base5)

Thicknet is similar in construction to Thinnet, however, there is an additional layer of aluminium insulation and copper braid. This means that the cable is more rigid and reliable and can be used for longer runs.

The thicker the copper core, the further the cable can carry signals. Thicknet is sometimes used as a backbone to connect several smaller thinnet based networks.

10base5 stands for:

  • Data Transmission Rate of 10Mbps, i.e. 10
  • Uses baseband transmission, i.e. Base
  • Used in Ethernet networks it has a maximum cable length of 500 metres, i.e. the 5 is for 500 metres

Thicknet Connections

Thicknet cable is connected to a network using a device called a transceiver. This device includes a piece of equipment that actually pierces the cable to connect to it. This connector is known as a vampire tap or a piercing tap. A computer’s NIC can then be connected to the transceiver using a special transceiver cable.

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