1. Net 222: Communications and networks fundamentals (Practical Part)
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Tutorial 3: Chapter 4 Data & computer communications

2. Chapter 4 page 135 (Data & computer communications)
Review questions:
4.1
4.3
4.4
Problems:
4.7
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3. Question 4.1. Why are the wires twisted in twisted-pair copper wire?
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4. Answer
The twisting of the individual pairs reduces electromagnetic interference. For example, it reduces crosstalk between wire pairs bundled into a cable.
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5. Question
4.3. What is the difference between unshielded twisted pair and shielded twisted pair?
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6. Answer
Unshielded twisted pair (UTP) is ordinary telephone wire, with no form of electromagnetic shielding around the wire. Shielded twisted pair (STP) surrounds the wire with a metallic braid or sheathing that reduces interference.
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7. Question 4.4. Describe the components of optical fiber cable.
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8. Answer
Optical fiber consists of a column of glass or plastic surrounded by an opaque outer jacket. The glass or plastic itself consists of two concentric columns. The inner column called the core has a higher index of refraction than the outer column called the cladding.
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9. Answer(Cont.)
4.7 The audio power of the human voice is concentrated at about 300 Hz. Antennas of the appropriate size for this frequency are impracticably large, so that to send voice by radio the voice signal must be used to modulate a higher (carrier) frequency for which the natural antenna size is smaller.
a. What is the length of an antenna one-half wavelength long for sending radio at 300 Hz?
b. An alternative is to use a modulation scheme, as described in Chapter 5, for transmitting the voice signal by modulating a carrier frequency, so that the bandwidth of the signal is a narrow band centered on the carrier frequency. Suppose we would like a half-wave antenna to have a length of 1 meter. What carrier frequency would we use?
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10. Question
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11. The End
Any Questions ?
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