13. Show the conventional symbols of a receiver.
14. Describe exactly how, in a cell composed of a tin and a silver plate with dilute sulphuric acid as electrolyte, the current inside and outside of the cell will flow.
15. Describe the phenomenon of polarization.
16. What is _local action_ of a cell? How may it be prevented?
17. Into how many cla.s.ses may cells be divided? Which cla.s.s is most used in telephony?
18. Describe the LeClanche cell.
19. Sketch and describe an excellent form of dry cell.
20. Show the conventional symbols for batteries.
21. Sketch and describe the generator shunt switch and the generator cut-in switch.
22. How may a pulsating current be derived from a magneto generator?
23. Show conventional symbols for magneto generators.
24. Sketch and describe the Western Electric polarized bell.
25. Give conventional ringer symbols.
26. What is the purpose of the hook switch?
27. Make sketch and give description of Kellogg"s long lever hook switch.
28. Describe and sketch the Western Electric short lever hook switch.
29. Point out the princ.i.p.al difference between the desk stand hook switches of the Western Electric Company and of the Kellogg Switchboard and Supply Company.
30. Give conventional symbols of hook switches.
REVIEW QUESTIONS
ON THE SUBJECT OF TELEPHONY
PAGES 143--225
1. Describe an electromagnet and its function in telephony.
2. Sketch an iron-clad electromagnet.
3. What is a differential electromagnet? Sketch and describe one type.
4. State the desirable characteristics of good enamel insulation for magnet wire.
5. If you have a coil of No. 23 double cotton B. and S. wire of 115 ohms resistance and you have to rewind it for 1,070 ohms resistance with double cotton wire, what number of wire would you take? Show calculation.
NOTE. No. 23 d. c wire has res. 1.772 ohms per cubic inch; for the core, 115 ohms. There are required in the coil 1,070 ohms, that is, 9.3 times as much. 1.772 x 9.3 = 16.47 ohms, which must be the resistance per cu. in. This resistance gives, according to Table IV, No. 29 wire.
6. What is an impedance coil? State how it differs from an electromagnet coil.
7. Describe the different kinds of impedance coils.
8. Give symbol of impedance coil.
9. What are the princ.i.p.al parts of an induction coil?
10. What is the function of an induction coil in telephony?
11. What is a repeating coil and how does it differ from an induction coil?
12. Give conventional symbols of induction coils and repeating coils.
13. Enumerate the different types of non-inductive resistance devices and give a short description of each.
14. Define condenser.
15. What is the meaning of the word _dielectrics_?
16. State what you understand by the specific inductive capacity of a dielectric.
17. Upon what factors does the capacity of a condenser depend?
18. What is the usual capacity of condensers in telephone practice?
19. Give conventional condenser symbols.
20. By what two methods may the current be supplied to a telephone transmitter?
21. Make sketch of local-battery stations with metallic circuit.
22. Sketch common-battery circuit in series with two lines.
23. State the objections against the preceding arrangement.
24. Make sketch of the standard arrangement of the Western Electric Company in bridging the common battery with repeating coils.
25. Sketch the arrangement of bridging the battery with impedance coils and state the purpose of the coils.
26. Make diagram of a common-source current supply for many lines with repeating coils and point out the travel of the voice currents.