Modules A-138p/o are used to built a simple performance mixer (instead of an external stand-alone mixer). Module A-138p is the 4-fold input module, A-138o is the output module that can be combined with one or more A-138p. The A-138p/o modules can be combined also with the voltage controller performance mixer modules A-135-4. A-138p features: 4 channels controls and inputs for each channel input (3.5 mm mono socket) signal LED (as a coarse monitor of the incoming level, the level is measured after the gain control) mute switch gain (control to adapt different audio levels) Level (the main volume control, linear response curve) Aux Pan internal jumper for each channel to choose between Aux pre/post main Level control internal connection to the output module and to other A-138p or A-135-4 modules A-138p requires A-138o (no stand-alone use)