3 computing system fundamentals
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3 Computing System Fundamentals. 3.4 Networked Computer Systems. 3.4.2 Network Hardware. The network interface. Computers may be directly connected to a LAN, in which case they will need special hardware (the network interface card or NIC ).

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3 Computing System Fundamentals

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3 Computing System Fundamentals

  • 3.4 Networked Computer Systems

3.4.2 Network Hardware

The network interface

  • Computers may be directly connected to a LAN, in which case they will need special hardware (the network interface card or NIC).

  • Even if they only connect occasionally to a WAN (e.g. using a dial-up connection via a telephone line) they need a modem.

  • Direct connections e.g. DSL are faster than dial-up connections.

Connection media

  • The medium of transmission may be:

    • an electrical cable (e.g. coaxial or unshielded twisted pair - UTP),

    • fibre optic cable or

    • via radio waves.

Coaxial cable

UTP cable

Fibre optic cable

Wifi base station

Microwave link

Satellite link

Network hardware

  • Various connection boxes co-ordinate the transmission of data with varying degrees of programability.

  • Of those that follow, the important ones are:

    • hub,

    • switch and

    • router.


  • A hub is a junction box, acts as a repeater, amplifying and sending on signals to networked devices, but not discriminating on where they are for or from.


  • A switch is similar to a hub but with some ability to filter out irrelevant traffic.


  • A bridge links together LANs, letting through only the data destined for that LAN (thus reducing unnecessary traffic).


  • A gateway is similar to a bridge, but can also translate data from one network protocol to another.


  • A router can translate and direct the traffic.

  • They are used to manage internet traffic: data will always be passed on to a router nearer to their destination.


  • A modem converts a computer’s digital data (stream of bits) to analogue (continuous wave) sound (DA conversion or DAC) and vice versa.


  • Dial-up modem speed theoretically up to 56kbps (bps = bits per sec).

  • ISDN (Integrates Services Digital Network), transfer rates of up to 144kbps).

  • ADSL (Asynchronous Digital Subscriber Line), incoming rate ~8Mbps and outgoing ~1Mbps).

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