To avoid any incorrect speculation, the white block in the middle of the Model 990 rear panel image is the plastic dust cap that is there to protect the USB jack. Also on the subject of covered jacks, there are two groupings of jacks on the right side of the front panel, covered by caps in the photo. the one on the left has an optical input and the jack for the set up microphone included with the unit. The jack pod on the right has the analog left/right audio, composite video and S-Video jacks for the "Video 5" input.