The system that takes calls coming into a big place — a company, a hotel, a hospital — and sends each one to the right person inside. Also the people who do that work: "call the switchboard and ask for Dr Lin", "switchboard put me through to accounts".

The picture behind the word is old. It really was a board covered in sockets, and an operator sat in front of it plugging a cable from your line into the line of the person you wanted. Those boards are gone, but the word stayed for the job they did, even now that a computer does the switching and a person just answers.

You will meet it most in phrases: the main switchboard, the switchboard number, a switchboard operator. There is also a nice everyday expression, "the switchboard lit up" — meaning huge numbers of people rang in at once, usually to complain or to react to something on the radio or television.

In electricity, the same word means a panel of switches that controls the power in a building. Same idea: one place where all the lines meet and get sent onward.