640 ZonePRO®6x4 Digital Zone ProcessorAdvanced Feedback Suppression (AFS™)Autowarmth®Auto Gain ControlCompressionLimitingNoise GatingNotch FilteringBandpass and Crossover FiltersParametric EQSecurity LockoutWall Panel ControlRS-232 ControlWindows® 2000 and XP GUIIEC, UL and CSA ApprovalsWith 6 inpu..