REVIEW QUESTIONS
REVIEW QUESTIONS
ON THE SUBJECT OF TELEPHONY
PAGES 11—62
1. When was the telephone invented and by whom?
2. State the velocity of sound in air. Is it higher in air than in a denser medium?
3. State and define the characteristics of sound.
4. Make sketch of Bell's original magneto telephone without permanent magnets.
5. Describe and sketch Hughes' microphone.
6. Which is, at present, the best material for varying the resistance in transmitters?
7. Give the fundamental differences between the magneto transmitter and the carbon transmitter.
8. What is the function of the induction coil in the telephone circuit?
9. Describe and sketch the different kinds of visible signals.
10. What should be the diameter of hard drawn copper wire in order to allow economical spacing of poles?
11. State the four principal properties of a telephone line.
12. If in testing a line the capacity is changed what are the results found on the receiver and transmitter end?
13. Why is paper used as an insulator of telephone cables?
14. How does a conductor behave in connection with direct current and how with alternating current?
15. What influence has inductance on the telephone?
16. Define impedance and give the formula for it.
17. What is the usual specification for insulation of resistance in telephone cables?
18. If 750 feet of cable have an insulation resistance of 9,135 megohms, how great is the insulation resistance for 7 miles and 1,744 feet of cable?
19. What is the practical limiting conversation distance for No. 10 B. and S. wire?
20. Describe Professor Pupin's method of inserting inductance into the telephone line.
21. What does mho denote?
22. Why are Pupin's coils not so successful on open wires?
23. What is a repeater?
24. Define reactive interference.
25. State the frequencies of the pitches of the human voice.
26. What is the office of a diaphragm in a telephone apparatus?
27. What transmitter material has greatly increased the ranges of speech?
28. Describe the different methods of measurements of telephone circuits.
29. What are the two kinds of electric calls?
30. How many conductors has a telephone line?
31. Give formula for capacity reactance and the meaning of the symbols.
32. Which American cities are joined by underground lines at present?
33. State the two practical ways of improving telephone transmission.
REVIEW QUESTIONS
ON THE SUBJECT OF TELEPHONY
PAGES 63—141
1. On what general principle are most of the telephone transmitters of today constructed?
2. Make sketch of the new Western Electric transmitter and describe its working.
3. Make sketch and describe the Kellogg transmitter.
4. What troubles were encountered in the earlier forms of granular carbon transmitters and how were they overcome?
5. What limits the current-carrying capacity of the transmitter? How may this capacity be increased?
6. State in what kind of transmitters a maximum degree of sensitiveness is desirable.
7. Show the conventional symbols for transmitters.
8. Describe a telephone receiver.
9. Sketch a Western Electric receiver and point out its deficiencies.
10. Make a diagram of the Kellogg receiver.
11. Describe the direct-current receiver of the Automatic Electric Company.
12. Describe and sketch the Dean receiver.
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 classes may cells be divided? Which class is most used in telephony?
18. Describe the LeClanché 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 principal 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 principal 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.
27. Name the different parts which comprise a telephone set.
28. What is a magneto telephone?
29. Make diagram of the circuit of a series magneto set with receiver on the hook and explain how the different currents are flowing.
30. Show diagram of the Stromberg-Carlson magneto desk telephone circuit and describe its working.
31. Give sketch of the Stromberg-Carlson common-battery wall set circuit.
32. Describe briefly the microtelephone set.
33. Make sketch of the Monarch common-battery wall set.
REVIEW QUESTIONS
ON THE SUBJECT OF TELEPHONY
PAGES 227—286
1. What is a party line?
2. What is usually understood by private lines?
3. What problem is there to overcome in connection with party lines?
4. State the two general classes of party-line systems.
5. Point out the defects of the series system.
6. Make sketch of a metallic bridging line and show the circuit for the voice currents.
7. What is a signal code?
8. Give classification of selective party-line systems with short definitions.
9. Describe the principle of selection by polarity and make sketch illustrating this principle.
10. Make diagram of the circuit of a four-party station with relay.
11. Describe the process of tuning in the harmonic system.
12. What is the difference between the under-tune and in-tune systems?
13. Sketch circuit of Kellogg's harmonic system.
14. Illustrate the principle of a broken-line system by a sketch.
15. In what particulars does the party-line system in rural districts differ from that within urban limits?
16. Describe and sketch Pool's lock-out system.
17. Make diagram of the K.B. lock-out system.
18. What is the object of the ratchet in this system?
19. Make diagram of simplified circuits of Roberts system.
20. Sketch and describe Roberts latching key and connections.
21. Sketch circuits of bridging station for non-selective party line.
22. How would you arrange the signal code for six stations on a non-selective party line?
23. What is the limit of number of stations on a non-selective party line under ordinary circumstances?
24. State the objections against the party polarity system as shown in Fig. 172.
25. What are the advantages of the harmonic party-line system?
26. To how many frequencies is the harmonic system usually limited?
27. What can you say about the commercial success of the step-by-step method?
28. State the principles of a lock-out party line.
29. For what purpose is a condenser placed in the receiver circuit of each station in the K.B. lock-out system?
30. How are the selecting relays in Roberts line restored to their normal position after a conversation is finished?
31. What are the objections against the Roberts system?
REVIEW QUESTIONS
ON THE SUBJECT OF TELEPHONY
PAGES 287—315
1. What are electrical hazards?
2. When is the lightning hazard least?
3. What actions can electricity produce? Which involves the greater hazard to the value of property?
4. When is a piece of apparatus called "self-protecting"?
5. Why must a protector for telephone apparatus work more quickly for a large current than for a small one?
6. State the general problem which heating hazards present with relation to telephone apparatus.
7. What is the most nearly universal electrical hazard?
8. Sketch and describe the saw-tooth lightning arrester.
9. Make diagram of the carbon-block arrester and state its advantages.
10. Describe a vacuum arrester.
11. Explain the reason for placing an impedance in connection with the lightning arrester.
12. What is the purpose of the globule of low-melting alloy in the Western Electric Company's arrester?
13. Why are not fuses good lightning arresters?
14. What is the proper function of a fuse?
15. Make sketch of a mica slip fuse.
16. Define sneak currents.
17. Make a diagram of a sneak-current arrester and describe its principles and working.
18. Describe a heat coil.
19. Sketch a complete line protection.
20. Where is the proper position of the fuse?
21. Which wires are considered exposed and which unexposed?
22. Why is it not necessary to install sneak-current arresters in central-battery subscribers' stations?
23. Sketch and describe the action of a combined sneak-current and air-gap arrester, as widely used by Bell companies.
24. Describe the self-soldering heat-coil arrester.
25. What is the purpose of ribbon fuses?
26. What is a drainage coil?
REVIEW QUESTIONS
ON THE SUBJECT OF TELEPHONY
PAGES 317—386
1. What is a central office?
2. What are (a) subscriber's lines? (b) Trunk lines? (c) Toll lines?
3. For what purpose is the switchboard?
4. Give short descriptions of the different classes of switchboards.
5. How are manual switchboards subdivided? Describe briefly the different types.
6. Define A and B boards.
7. What is a call circuit?
8. What kind of calls are handled on a toll switchboard?
9. Give drop symbol and describe its principles.
10. What is a jack?
11. Make a sketch of a plug inserted into a jack.
12. Give jack and plug symbols.
13. What are ringing and listening keys?
14. Show symbols for ringing and listening keys.
15. State the parts of which a cord equipment consists.
16. Show step by step the various operations of a telephone system wherein the lines center in a magneto switchboard. Make all the necessary diagrams and give brief descriptions to show that you understand each operation.
17. On what principle does a drop with night-alarm contact operate?
18. What is the advantage of associating jacks and drops?
19. Describe the mechanical restoration as employed in the Miller drop and jack.
20. Describe the electrical restoration of drop shutters as manufactured by the Western Electric Company.
21. What complications arise in ringing of party lines and how are they overcome?
22. Give diagram of the complete circuit of a simple magneto switchboard.
23. Sketch night-alarm circuit with relay.
24. What is a convertible cord circuit?
25. State what disadvantages may be encountered under certain conditions with a bridging drop-cord circuit.
26. Are lamps in cord circuits to be advocated on magneto switchboards?
27. What is the function of the cabinet?
28. Give cross-section of upright switchboard as used in the magneto system.
29. What is the purpose of a sectional switchboard?
30. Give a short description of the essential parts of a sectional switchboard.