AC-3 signals: The analogue Dolby Surround supplies the two rear surround boxes with the same sound effects. The digital AC-3Signal on the other hand, contains for each speaker the surround system own information provided to them by the AC-3Decoder via six discrete channels. Result: More elaborate effects, like a shot blasting across the room. In addition, the digitally delivered Ton a higher sound quality. Dolby Digital-Signals currently only deliver DVDs and Laserdiscs.