Telephone switchboards allow the operator to plug an incoming caller's phone line into the correct circuit. Thus, the incoming call connects to the correct destination.
The incoming caller's line terminates in a jack. In order to connect that line to the needed destination, the electric circuit has to be completed. This is accomplished when the switchboard operator places the jack in the corresponding hole. This leads to the phone ringing at the destination phone.
The first telephone switchboard was designed in 1877, shortly after the invention of the telephone. The first model was made in Boston. This device was created in order to accommodate the complicated needs of connecting multiple landlines all using hard wires.
As of 2015, switchboards are designed to accomplish similar goals to the original models, but operators no longer need to manually plug in wires in order to make the needed connections. Modern systems are largely computerized. Businesses rely heavily on this sort of technology today, especially in the customer service sector.
Telephone operators today are often required to both direct incoming calls and act as a receptionist. This includes working the computerized switchboard, as well as greeting the in-office customers and helping them find their destination.