Review Questions

1. What is meant by the terms single-current and neutral telegraph systems?

2. Explain the difference between open-circuit and closed-circuit systems.

3. What are the average and maximum rates of manual, or Morse, operation?

4. If perfectly rectangular impulses such as shown in Fig. 3 are transmitted, what will be the maximum alternating frequency components present?

5. About what are the maximum frequency components transmitted in an average telegraph channel?

6. In modern practice what type of relays are used in single-current systems?

7. Explain the operation of the double-current or polar telegraph system.

8. Give several reasons why the polar system is preferable.

9. What two types of duplex systems have been developed, and what type usually is employed at present?

10. Explain the basic principle of the start-stop teletypewriter.

11. Explain the basic principle of the multiplex system.

12. Could a hand-operated teletypewriter operate directly into a multiplex system ?

13. Why are perforated tapes used with multiplex operation?

14. What is meant by the term telegraph channel? Name several systems that provide multichannel operation over one grounded line.

15. Briefly discuss the two possible bases for analyzing telephone transmission. Which is usually employed?

16. What is meant by the word baud?

17. If 60 words per minute will produce a third harmonic of about 75 cycles, why are wider channels sometimes provided for telegraph service?

18. Why is bias distortion so very important in telegraphy? Does this have any bearing on the use of the polar system?

19. Name and distinguish between the several types of distortion.

20. What two functions are performed by regenerative repeaters? What types are used?

21. Briefly explain the basic principle of the varioplex system. Will it operate into multiplex equipment? Into carrier telegraph systems?

22. What types of carrier telegraph systems are used? Which type is most widely used in the Bell System? In Western Union systems? Can you give reasons for this?

23. Describe the amplitude-modulation telegraph system.

24. Describe the frequency-modulation telegraph system.

25. Describe the teletypewriter exchange system.

26. What is meant by reperforator switching?

27. Briefly describe the means by which simultaneous telephone and telegraph service are given over the same circuits.

28. Why is the so-called metallic telegraph system of increasing importance?

29. Explain the difference between the telefax and teletape systems.

30. Briefly describe methods of giving transoceanic telegraph service over cables.