Page 190 - Computer_Science_F5

(c) It can be used for analogue or Coaxial cable
digital transmission. Coaxial cables are commonly used by cable
(d) It increases the signalling rate. TV, telephone companies, and computer Chapter Three: Advanced Computer Networks
(e) It has a higher capacity than an networks for transmitting data. It is better
unshielded twisted pair. shielded and has more bandwidth than a
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(f) It eliminates crosstalk. twisted pair. It has a copper wire as the
core, which is surrounded by insulating

Disadvantages of shielded Twisted Pairs material as see in Figure 3.35. The coaxial
cable contains two conductors that are
(a) It is difficult to manufacture. parallel to one another. Copper is used
(b) It is heavy. as a centre conductor, a solid wire, or a
(c) It is expensive. standard one.

Inner conductor
Insulator
Outlet conductor Jacket Plastic cover
(Shield)

Figure 3.35: A coaxial cable

It is surrounded by Polyvinyl Chloride (PVC) installation encased in an outer
conductor of metal foil, braid, or both. Outer metallic wrapping is used as a shield
against noise and as the second conductor that completes the circuit. The outer
conductor is also encased in an insulating cover; the outer part is the plastic cover
which protects the whole cable. The most common coaxial standards are:

(a) 50-Ohm RG-7 or RG-11 is used with a thick ethernet.
(b) 50-Ohm RG-58 is used with athin ethernet.

(c) 75-Ohm RG-59 is used with cable television.
The key to the success of coaxial cable is its shielded design that allows
the cable’s copper core to transmit data quickly, without the interference of
environmental factors. These types of cables are used to carry signals of higher
frequencies to a longer distance

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Student’s Book Form Five

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