A walkie-talkie is a portable two-way radio set developed by the United States Army Signal Corps in 1933 and employed extensively during World War II by the infantry for communication between platoon and company commanders. It weighed about 30 pounds, had a telescoping antenna and French-type telephone, and was worn strapped to the back of a soldier who remained at the side of his unit commander. Both the transmitter and receiver operated on one preset frequency, thus eliminating tuning, and were automatically switched on when the antenna was extended to its full leng'th.
Following the war, the size was greatly reduced by the development, first, of small batteries and tiny vacuum tubes and, later, of transistors and other miniaturized parts. Combination transmitters and receivers, now called transceivers, have since found many police, fire, railroad, trucking, and other civilian applications in addition to their military use.