Abstract :
The growth of the telephone network in the United States since the 1920´s has been rapid and continuous. This expansion has been achieved largely through the application of carrier techniques. Most of the carrier systems, in addition to providing a number of voice bandwidth circuits, also have the capability of providing circuits of wider bandwidths. Through the years there has been a steady increase in the number and variety of communication services that require these wider bandwidths. These wideband services, as they are generally called, include telemetry, data, and graphic systems. Their evolution is traced and their technical requirements are briefly discussed.
