A vocoder (/ˈvoʊkoʊdər/, short for voice encoder) is a category of voice codec that analyzes and synthesizes the human voice signal for audio data compression, multiplexing, voice encryption, voice transformation, etc. The earliest type of vocoder, channel vocoder was originally developed as a speech coder for telecommunications applications in the 1930s, the idea being to code a speech for reducing bandwidth (i.e. audio data compression) for multiplexing transmission.