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.