A switchboard is a piece of equipment used for connecting and disconnecting telephone calls.
Switchboards used to be operated by people, but now they are mostly automated.
Examples:
The operator connects the call using the switchboard.
The old switchboard had lots of wires.
The switchboard is an important part of the telephone system.
The switchboard beeped and lit up with lots of little lights.
In the past, switchboards were used to connect calls manually.
The switchboard hummed quietly in the corner of the room.