Download Information Technology Unit 2

Information Technology Unit 2
Ch 7, Networks
Network Classification, Network Hardware and how networks are
connected, p 222-231
Communications Devices
1
What is a communication device?
A communications device is any type of hardware capable of
transmitting data, instructions or information between a sending
device and a receiving device. Common examples include modems
and network interface cards.
Modems
1 Describe the nature of a modem.
Both sending and receiving ends of a communications channel must
have a modem fro data transmission to occur.
2 List examples of digital modems.
 ISDN
 DSL
 Broadband
 Cable
Network Interface Cards, (NIC)
1 Describe the nature of a NIC.
A network interface card is a card you insert into an expansion slot of a
personal computer or other device, such as a printer, enabling the device
to connect to a network.
2 What are the functions of this device?
The NIC coordinates the transmission and receipt of data, instructions
and information to and from the computer or device containing the NIC.
Wireless access point, (WAP)
1 Describe the nature of a WAP.
A wireless access point is a central communications device that allows
computers and devices to transmit data wirelessly among themselves.
Hubs, Routers & Switches
1
2
What is a hub?
A hub is a device that provides a central point for cables in a star
LAN.
Describe the role of a router.
A router directs a packet it receives down all available cables. The
packet is therefore received by all devices attached to the hub, but
only the device identified in the address of the packet will read the
packet.
D:\478179285.doc
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4
Describe the nature of a switch.
A switch stores the address of every device down each cable
connected to it.
What technology has switches replaced?
Switches also largely replace hubs in star networks, since the price
difference is low and the added efficiencies of a switch make it a
logical choice for many networks.
Communications Channels
1 What is the channel?
A channel is a communications path between two devices.
2 Define bandwidth.
Bandwidth is the width of the communications channel. The higher the
bandwidth, the more data and information the channel can transmit.
3 What are the 2 types of transmission media?
Transmission media consist of materials or techniques capable of
carrying one or more signals. There are baseband media which can
transmit only one signal at a time and there is broadband media which
signals at a much faster speed than those that use baseband.
Physical Transmission Media
1
2
3
4
5
6
7
What is twisted pair cable and list its different transfer rates.
Twisted-pair cable systems are graded according to categories that
describe the quality of the components and the installation technique.
Its transfer rates are 10Mbps, 100Mbps, 1Gbps, and 4Mbps-16Mbps.
Describe the nature of coaxial cable.
Coaxial cable consists of a single copper wire surrounded by at least
three layers: 1) an insulating material, 2) a woven or braided metal
and 3) a plastic outer coating.
What is the transfer rate of coax?
10Mbps
Why is coax less popular for networks today?
Because other transmission media, such a fibre-optic transmit signals
at faster rates.
Describe the nature of fibre-optic cable.
The core of a fibre-optic cable consists of dozen or hundreds of thin
strands of glass or plastic that use light to transmit signals.
List the advantages of fibre-optic over other cable and wireless
transmission.
 The capability of carrying significantly more signals than wire
cables
 Faster data transmission
 Less susceptibility to noise (interference) from other devices, such
as a copy machine
 Better security for signals during transmission, as they are less
susceptible to noise
 Their smaller size (much thinner and lighter in weight)
List the disadvantages of fibre-optic.
The disadvantages of fibre-optic cable are that it costs more than
twisted-pair or coaxial cable and it can be difficult to install and
modify.
Wireless transmission media
Broadcast radio
1
2
3
4
Describe the nature of broadcast radio.
Broadcast radio is a wireless transmission medium that distributes
radio signals through the air over long distances.
Describe Bluetooth technology.
Bluetooth uses short-range radio waves to transmit data among
Bluetooth-enabled devices. A Bluetooth-enabled device contains a
small chip that allows it to communicate with other Bluetooth-enabled
devices.
What is the transfer rate of Bluetooth?
1Pbps-2Mbps
To communicate using Bluetooth what is necessary?
You must have a small chip that enables you to connect to other
Bluetooth-enabled devices.
Cellular Radio
1
2
3
Describe the nature of this technology?
Cellular radio is a form of broadcast radio that is used widely for
mobile communications, specifically wireless modems and mobile
telephones.
What devices use this technology?
A mobile phone, web
List the transfer rates of this technology.
9.6Kbps-19.2Kbps
114Kbps-2Mbps
Microwaves
1 Describe the nature of microwave transmission.
Microwave transmissions are often a viable alternative to cabling where
an organisation has premises on different sides of a mayor road/. The
cost of diffing a tunnel under the road can be expensive and repairs
difficult if there is a break.
2 What is a microwave station?
A microwave station is an Earth-based reflective dish that contains the
antenna, transceivers and other equipment necessary for microwave
communications.
3 What type of transmission do microwaves use?
Microwaves use line-of-sight transmission, which means that microwaves
must transmit in a straight line with no obstructions between microwave
antennas.
4 Where is microwave transmission used?
Microwave transmission is used in environments where installing
physical transmission media is difficult or impossible and where line-ofsight transmission is available.
Communications satellite
1 Describe the nature of a communications satellite.
A communications satellite is a space station that receives microwave
signals from an Earth-based station, amplifies the signals and broadcasts
the signals back over a wide are to any number of Earth-based stations.
2 List the applications that use communications satellites.
Applications such as air navigation, television and radio broadcasts,
videoconferencing, paging and global positioning systems use
communications satellites.
Infra-red, IrDA
1
2
3
Describe the nature of IrDA transmission.
IrDA is a wireless transmission standard that sends signals using
infra-red light waves.
What does IrDA transmission require?
Infra-red transmission requires a direct line of sight between the
sending device and the receiving device.
What is the data transfer rate of IrDA?
Current data transfer rates for the IrDA standard are between
115Kbps and 4Mbps