Before new fangled digital telephone exchanges, people had to have their calls connected by hand. Telephone exchanges would have teams of switchboard operators (usually women as men were found to not have the patience and personal skills to deal with the general public!)
The operator had a high panel in front of them with rows and rows of female jacks (holes basically). When a telephone user made a call then one of the lamps above a jack would light up. The operator would insert a plug into the jack to speak to the caller and find out whom they wanted to call. The operator would then insert another plug into one of the other jacks to complete the circuit and allow the call to be made.
Although this worked well it did not scale and was quickly overwhelmed by demand, especially in big cities were there were soon thousands of telephone lines by the early 1900s. Automatic exchanges began operating in Britain in 1912 though the last manual exchanges were not turned off until the 1960s, and continued in use on a smaller scale in internal business switchboards for longer.
Below are two examples of this kind of exchange switchboard seen in the Birmingham Museum collection.
