The phantom power circuit is only on the XLR mic input. The line switch swaps the channel input between the XLR inputs and the line inputs (25 pin connector). Then the signal passes through the fader, filter and dynamics (compressor then limiter) and is then split so that one feed goes to the line outs (25 pin connector) and the other to the A/D converter. On channel one the input is switchable between the instrument input too and there is a phase reverse circuit before the filter.