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.