Complex sentence: It should be noted that four-wire systems are essentially audio routers, which makes them very useful not only for the communications aspect of a production, but also routing of audio for confidence monitoring or actual on-air use.
Split into simpler sentences: It should be noted that four-wire systems are essentially audio routers. This makes them very useful not only for the communications aspect of a production, but also routing of audio for confidence monitoring or actual on-air use.