1. NET 222: COMMUNICATIONS AND NETWORKS FUNDAMENTALS ( NET 222: COMMUNICATIONS AND NETWORKS FUNDAMENTALS (PRACTICAL PART) Tutorial 3 : Chapter 4 Data & computer communications Networks and Communication Department 1

2. Chapter 4 page 135 (Data & computer communications) Networks and Communication Department 2  Review questions:  4.1  4.3  4.4  Problems:  4.7

3. Question Networks and Communication Department 3  4.1. Why are the wires twisted in twisted-pair copper wire?

4. Answer Networks and Communication Department 4  The twisting of the individual pairs reduces electromagnetic interference. For example, it reduces crosstalk between wire pairs bundled into a cable.

5. Question Networks and Communication Department 5  4.3. What is the difference between unshielded twisted pair and shielded twisted pair?

6. Answer Networks and Communication Department 6  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.

7. Question Networks and Communication Department 7  4.4. Describe the components of optical fiber cable.

8. Answer Networks and Communication Department 8  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.

9. Answer(Cont.) Networks and Communication Department 9  4.7 The audio power of the human voice is concentrated at about 300 Hz. Antennas are used to send voice by radio.  a. What is the length of the wave of an antenna which is one-half the wavelength needed for sending radio at 300 Hz?  b. Suppose we would like a half-wave antenna to have a length of 1 meter. What frequency would we use?

10. Question Networks and Communication Department 10

11. Any Questions ? The End 11 Networks and Communication Department