Complex sentence: Ahead of its time, the 840AV and its relative, the Centris/Quadra 660AV, were the first Macintoshes to include 16-bit 48KHz stereo audio recording capability, as well as S-Video and Composite video input and output.
Split into simpler sentences: Ahead of its time, the 840AV and its relative, the Centris/Quadra 660AV, marked a number of firsts for the Macintosh family. They were the first Macintoshes to include 16-bit 48KHz stereo audio recording capability, as well as S-Video and Composite video input and output.