The TOA M-864D CU is a 4U rack-mount digital stereo mixer engineered for permanently installed audio environments including hotel banquet rooms, multipurpose halls, and conference facilities that regularly change event formats. Its 8 monaural and 7 stereo input channels, paired with a 12x4 matrix and five output channels, give installed-sound engineers the routing flexibility to address varied program sources without external patch hardware. The analog-feel fader design and 14 physical volume controls mean front-of-house staff can manage a live event without opening a laptop, while Ethernet connectivity and companion GUI software give system integrators the fine-tuning access they need during commissioning or remote adjustments. What sets the M-864D CU apart from generic installed-sound DSPs is its onboard proprietary Automatic Resonance Control technology, which generates output EQ curves automatically without requiring an acoustic measurement instrument. Combined with per-channel Feedback Suppressor filtering on each of the eight monaural inputs and a three-band tone controller with a parametric mid available on every input channel, the mixer handles room acoustics and gain-before-feedback in venues where a dedicated engineer may not always be present. Sixteen preset memories allow room configurations to be recalled instantly for different event types, making this unit a strong alternative to separate DSP-plus-mixer combinations in integration projects where rack space and operational simplicity are priorities.