0567--Data Communication and Networking

8/6/2019 0567--Data Communication and Networking

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Data Communication andData Communication and

NetworkingNetworkingData communication is the process ofData communication is the process of

transferring information from one point totransferring information from one point to

another. It consists of three basic elements,another. It consists of three basic elements,

which are:which are:

1.Transmitter:1.Transmitter: is the source of information or fromis the source of information or from

where information is sent.where information is sent.

2.Medium:2.Medium:Which carries information such asWhich carries information such astelephone lines, coaxial cables, fiber optics.telephone lines, coaxial cables, fiber optics.

3.Receiver:3.Receiver: it receive information.it receive information.


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Modes of Data CommunicationModes of Data Communication

The mode of transmission used depends uponThe mode of transmission used depends upon

the type of terminal used in the datathe type of terminal used in the data

communication network and the speed atcommunication network and the speed at

which data must be transmitted. There arewhich data must be transmitted. There arethree modes of transmission:three modes of transmission:

1.Simplex:1.Simplex:

It is capable of transmitting data in only oneIt is capable of transmitting data in only onedirection.i.e unidirectional. Radio anddirection.i.e unidirectional. Radio and

television broadcasting are examples oftelevision broadcasting are examples of

simplex transmission.simplex transmission.


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2.Duplex2.DuplexIn this type , data is transmitted in bidirectionalIn this type , data is transmitted in bidirectional

way. Duplex is further divided into two types:way. Duplex is further divided into two types:

a. Half Duplex:a. Half Duplex:

In this type, data is transferred in bothIn this type, data is transferred in both

directions but one at a time. Wireless set is andirections but one at a time. Wireless set is an

example of halfexample of half--duplex .duplex .

b. Full Duplex:b. Full Duplex:

In this type, data is transferred in both directionsIn this type, data is transferred in both directions

simultaneously. Examples are telephone linessimultaneously. Examples are telephone lines


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Communication speedCommunication speed

Bandwidth describes the data communicationBandwidth describes the data communicationcapacity of a communication system. It iscapacity of a communication system. It isrange of frequencies available for therange of frequencies available for thetransmission of data.transmission of data.

The data communication is measure in a unitThe data communication is measure in a unitcalled baud. In general, baud as same ascalled baud. In general, baud as same asnumber of bits transmitted per second. Itnumber of bits transmitted per second. Itclassified into three categories:classified into three categories:

a. Low speed or Narrow Banda. Low speed or Narrow Band

b. Medium Speed or Voice Bandb. Medium Speed or Voice Band

c. High speed orBroadbandc. High speed orBroadband


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Communication speed (cont)Communication speed (cont)

a. Low Speed or Narrow band:a. Low Speed or Narrow band:It transmits data at a range of 45It transmits data at a range of 45--300.Telegraphic300.Telegraphic

system is an example of this speed.system is an example of this speed.

b. Medium Speed or Medium band:b. Medium Speed or Medium band:

It transmit data at a rate varying from 300 to 56,000It transmit data at a rate varying from 300 to 56,000baud. Fax machine work on voice band systems.baud. Fax machine work on voice band systems.

c.Broad Band:c.Broad Band:

It transmits data at a very high baud rate of 1 million.It transmits data at a very high baud rate of 1 million.Microwave communication is an example of this.Microwave communication is an example of this.


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Medium of TransmissionMedium of TransmissionFollowing are the different medium ofFollowing are the different medium of

transmission:transmission:

1.Cable Medium1.Cable Medium

2.Cable less Medium2.Cable less Medium

1.Cable Medium: is further divided into :1.Cable Medium: is further divided into :

a. Twisted pair cable:a. Twisted pair cable:

It is a copper wire twisted together and used forIt is a copper wire twisted together and used for

short distance communications and datashort distance communications and datatransmission speed is up to 9600 baud. They aretransmission speed is up to 9600 baud. They arecommonly use in telephone system. Its furthercommonly use in telephone system. Its furtherdivided into shielded twisted pair(STP) anddivided into shielded twisted pair(STP) andunshielded twisted pair(UTP).unshielded twisted pair(UTP).


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Medium of Transmission (cont)Medium of Transmission (cont)

b. Coaxial Cable:b. Coaxial Cable: It contains a single central wire,It contains a single central wire,surrounded by special insulation and wire mesh. Itsurrounded by special insulation and wire mesh. It

is capable of transmitting data 10 mega bits peris capable of transmitting data 10 mega bits per

second. It used in long distance telephone lines.second. It used in long distance telephone lines.

c. Fiber Optic:c. Fiber Optic: It contains a hair thin strand of opticalIt contains a hair thin strand of opticalfiber made of glass or plastic, surrounded byfiber made of glass or plastic, surrounded by

special shielding and insulation. Optical fiber opticsspecial shielding and insulation. Optical fiber optics

carries pulses of light instead of bursts ofcarries pulses of light instead of bursts of

electricity. Converters are use at the ends of theseelectricity. Converters are use at the ends of these

fibers, which convert light waves into electricity andfibers, which convert light waves into electricity and

electricity into light waves.electricity into light waves.


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2.Cableless Medium2.Cableless MediumIt also further divide into two types:It also further divide into two types:

a. Microwave Transmission:a. Microwave Transmission:

Microwave transmission signals travelMicrowave transmission signals travelthrough open space much like radio signals.through open space much like radio signals.

This system transmit information withThis system transmit information withtransmitters which are normally installed ontransmitters which are normally installed onhigh buildings, mountain tops or highhigh buildings, mountain tops or hightowers. Long distance channels consist of atowers. Long distance channels consist of a

series of rely stations boosters) spacedseries of rely stations boosters) spacedapproximately 30 miles away apart. Theyapproximately 30 miles away apart. Theyamplify signals. Two stations must be withinamplify signals. Two stations must be withinsight of one another.sight of one another.


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2.Cableless Medium (Cont)2.Cableless Medium (Cont)

b.Communication satellites:b.Communication satellites:Satellites are lunch by rockets in a spaceSatellites are lunch by rockets in a space

approximately 22,000 miles above the earth. Theseapproximately 22,000 miles above the earth. These

satellites act as a rely stations for the transmissionsatellites act as a rely stations for the transmission

of signals generated from earth.of signals generated from earth.

Earth stations consisting of ground antennas beamEarth stations consisting of ground antennas beam

signals to satellite.The satellite amplifies andsignals to satellite.The satellite amplifies and

retransmits the signal to another earth station whichretransmits the signal to another earth station which

can be located many thousand of miles away. Itcan be located many thousand of miles away. It

revolve around its orbital with a uniform speed ofrevolve around its orbital with a uniform speed of

earth to overcome the problem of lineearth to overcome the problem of line-- ofof--sight.sight.

0567--Data Communication and Networking

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