Review Questions

1. Discuss the original Hartley law, and its modifications.

2. If a given bandwidth is available, what effect will a high signal-to-noise power ratio have on the number of messages that can be successfully transmitted? On the quality of a limited number of messages?

3. What relations exist between frequency modulation and the modified Hartley law?

4. What are the effects of interference in wire transmission systems?

5. Why do copper oxide varistors, connected across operators' telephone sets, reduce acoustic shock?

6. What is meant by the statement (page 542) that noise masks speech and signal currents?

7. What is meant by induction, inductive interference, and inductive coordination?

8. Discuss the nature of the factors determining interference between wire lines.

9. In Fig. 5 and subsequent figures, voltages to ground are represented by generators. If, in calculations, the internal impedance of these fictitious generators must be considered, what will be its nature?

10. What are meant by the terms series unbalance, and unbalance to ground? Give a practical example of each.

11. Why must transpositions in a telephone line be reasonably close together?

12. Explain the difference between balanced and residual components.

13. Name several methods of reducing interference from generators with grounded neutrals.

14. What is the difference between triple harmonics and non-triple harmonics? Which are the more bothersome? Why?

15. How may the magnitudes of triple and non-triple harmonics be controlled?

16. What is meant by TIF? Describe a meter for measuring it,

17. What effect do balanced voltages have on paralleling conductors? What effect do balanced currents have?

18. What effect do residual voltages have on paralleling conductors? What effect do residual currents have?

19. Prom the standpoint of noise interference, what is the fundamental difference between balanced and unbalanced telephone circuits?

20. What is the difference between near-end crosstalk and far-end crosstalk?

21. What is meant by plant protection? What hazards exist for telephone and telegraph plant? For radio systems?

22. Why is it necessary, at times, to protect buried cables against lightning?

23. How can a direct-current street railway system cause trouble to underground telephone and telegraph systems?

24. What are the fundamental principles of reducing interference from electric equipment?

25. What is meant by radio interference, and what types are of importance?

26. What are the causes of, and remedies for, atmospheric noise? Why is it less bothersome at very high frequencies?

27. What is electrical noise, and what are some of its causes?

28. How can a direct-current trolley system cause noise in telephone and radio systems?

29. What is precipitation static? What are the causes and successful remedies? Will precipitation static be experienced with jet planes? Why?

30. Describe a radio noise meter.