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.