Communications Channel

Question 1

Wire-Pairs

Answer 1

They are very simple link between transmitter and receiver

-Applications ; linking doorbell in a house to the witch outside the door

Question 2

Coaxial Cables

Answer 2

Application :- They are used to connect an aerial to a television receiver

Question 3

Radiowaves

Answer 3

1-The alternating current in a wire acts as an aerial where energy is radiated from the aerial int he form of electromagnetic waves
2-Aerials with dish reflectors enables the radio waves to be transmitted as a parallel beam
3-The intensity of the radio waves will be reduced as the distance from the transmitter increases
4-The degree of attenuation depends on the frequency
Application fm to am broadcast

Question 4

Microwaves

Answer 4

• They are electromagnetic waves that can be considered alongside radio waves
• They are used for point to point communications since transmission on earth is limited to line of sight

Question 5

Optic fibres

Answer 5

• It consist of a fine strand of very pure glass, surrounded by a protective covering
• pulses of light or infra red radiation travel along the fibre as a result of total internal reflection

Question 6

Optic Fibre advantages

Answer 6

• Large Bandwidth giving rise to large transmission capacity
• Diameter and weight of cable is much less than metal cables
• Much less signal attenuation, so fewer regenerator amplifiers are needed

Question 7

Communication satellite (disadvantage)

Answer 7

1- Long distance communication are unreliable because it depends on the reflection of ions in the upper atmosphere which vary of heights
2-Wave bands available are narrow and unable to carry large amounts of information