Sony MSW-900 Operation Manual page 28

MONITOR switch
This switch selects the audio output to the speaker or earphone.
2
CH-1/2 CH-3/4
position
CH-1/2
CH-3/4
2-12
Chapter 2 Locations and Functions of Parts and Controls
MONITOR switch
position
CH-1
MIX
CH-2
CH-3
MIX
CH-4
Audio output
Audio channel 1
Mix sound of channels 1 and 2
Audio channel 2
Audio channel 3
Mix sound of channels 3 and 4
Audio channel 4