Each RM-MP12 input may be individually calibrated for unbalanced consumer, balanced professional, 8 Ohm speaker line or constant voltage speaker lines. There is a variable intensity LED on the front panel to show audio presence for each input. If the RM-MP12 is set to the interlocking operating mode, front-panel pushbuttons select one of the twelve inputs to feed the calibrated meter, front-panel speaker (or external speaker if connected) and headphone jack. In the mixing mode, the buttons allow the use to mix multiple sources. The front-panel volume knob controls the audio level of the front-panel headphone jack, front-panel speaker, external speaker output and variable line level (+4 dBu) rear-panel output. A separate fixed line-level output is provided.