Digital sound audio.
I think the sound systems come in many different variations, some are big and some are small. The two types of sound systems are fixed or portable. Both have unique characteristics that are based on the application they are intended for. While a large sound system may cover thousands of people. While a large sound system may cover thousands of people. Other things that optical Audio or Toslink is a digital audio. It or the usually orange RCA jack, which is an also digital audio, are the best ways to get audio information into a receiver.
Thanks lot advance