The forms of communication in the 1940s were verbal, written and electromechanical. In the 21st century, they are verbal, written and electronic. The changes that have occurred in the past 60 years in the types of communication are the result of the technological advances that began with the invention of the transistor at Bell Laboratories in 1947.
In the 1940s, people spoke face to face. They also received, in groups, communications from teachers, preachers, politicians, sports announcers and salesmen. Often these messages were amplified by loudspeakers. Other communications came through broadcast radio. Two-way radio communications were coming into use for agencies such as police departments as the result of World War II military uses. Large numbers of people, businesses, agencies and institutions were using telephones for increasingly convenient and inexpensive communications.
Written letters and cards maintained communications between people separated by the movements caused by World War II and the postwar social and economic changes. U.S. mail was delivered twice a day on weekdays until 1950. Airmail service was available at extra cost as the closest thing to overnight delivery.
Written wide-distribution communications were conveyed by newspapers, magazines and books. Many people had available morning and evening newspapers published independently and often in fierce competition.
Television broadcasting began on a very limited scale in the 1940s but most visual communication was done through movies. Newsreels and short-subject films communicated news, particularly war news, and instructional information to audiences gathered for entertainment.
The U.S. Navy used signal lights and semaphore flags for short-range visual communication. Two semaphore flags positioned in various ways indicated letters, numbers and symbols. The signal lights used shutters attached to spotlights to allow the sender to send shorter and longer flashes of light. These were the dots and dashes of the Morse code used by the telegraph system.
In addition to the telephone, the telegraph and the teletype were other types of electromechanical communication used in the 1940s. Telegrams sent by individuals, generally on the Western Union system, were charged for by the word and so tended to be used only for the most urgent communications.
Teletype machines were largely mechanical devices that automated telegraphy. A machine like a typewriter was used to input the communication and on the receiving end it was typically printed out on a paper tape. They were used by newspapers to receive breaking news regarding disasters, wars, and other very time-sensitive communications such as sports and stockmarket reports.