Broadcasting is the distribution of audio and/or video content to a dispersed audience via any electronic mass communications medium, but typically one using the electromagnetic spectrum (radio waves), in a model. Broadcasting began with AM radio broadcasting which came into popular use starting with the invention of the crystal detector in 1906. Before this, all forms of electronic communication, radio, telephone, and telegraph, were "one-to-one", with the message intended for a single recipient. The term "broadcasting", borrowed from the agricultural method of sowing seeds in a field by casting them broadly about, was coined by either KDKA manager Frank Conrad or RCA historian George Clark around 1920 to distinguish this new activity of "one-to-many" communication; a single radio station transmitting to multiple listeners.