ABSTRACT
Signal processing arose with the design of sending and receiving equipment for long undersea telegraph cables in the last third of the 19th century. Starting in the early 20th century, telephone companies, especially the Bell System in the United States, turned to early electronics in the form of vacuum tubes to improve the range, reliability, and bandwidth of telephone circuits. The distinction between analog and digital signals was, of course, moot before the harnessing of electricity to transmit information. Signals received by the mirror galvanometer were ephemeral—receiving operators and engineers could deduce little about the sharpness and strength of the incoming signals. The advent of a self-defined profession of signal processing occurred only during the mid-1960s after sufficient computing power became available. Quite simply, signal processing required the integrated circuits (ICs) and the resulting miniaturization of electronics.
