Pioneer CD-MC20 Auto-EQ Microphone for Car DVD Receivers Function:The CD-MC20 Auto-EQ microphone automatically measures your car's interior acoustic characteristics, and allows your compatible Pioneer Audio/Video receiver to create an auto-equalizer curve based on that information. Placement:The Pioneer CD-MC20 Auto-EQ microphone should be placed in the center of your vehicle's driver seat headrest facing forward. Connection:The Pioneer CD-MC20 Auto-EQ microphone features an attached 6.5' cable terminated by a male 3.5mm connector which plugs into an auxiliary input on your compatible Pioneer A/V receiver. Automatically measures your car's interior acoustic characteristics The Pioneer CD-MC20 Auto-EQ microphone features an attached 6.5' cable terminated by a male 3.5mm connector