Early telephones had no dial. You picked up the earpiece and turned a handle, This alerted an operator at the telephone exchange who plugged a cable into a jack. You could then tell the operator the number that you wanted to connect to and the operator plugged another cable into that customer’s jack. In the case of long-distance calls, the operator plugged the cable into a “trunk” line to connect to another operator at the distant exchange.
One problem with this system was that operators were sometimes induced by businesses to redirect competitor’s calls to them or to favour them if the instructions were vague (such as “connect me to a taxi company”).
In about 1888, Almon Brown Strowger, an undertaker, became convinced that his business was losing clients to a competitor whose telephone-operator wife was intercepting and redirecting everyone who called Strowger. He solved the problem by inventing an electromechanical rotary dialing system which did away with the need for an operator when making simple calls. (An operator was still required to connect long-distance calls until subscriber trunk dialing was introduced in the 1960s.)