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.