With the introduction of Dolby Surround 7.1 in 2010, Sony were eager to put out a full home theater system. One of their early models, the HT-A7.100, included a revolutionary evolution to the standard stereo jack: the 7.1 surround jack, allowing all 8 channels to be sent over one cable.
@mia TRRRRRRRS it's also the sound it makes when you plug/unplug it with the speakers turned on