Better saying about the connections:This buttom allows me to work with two different settings. In the back side the cable passes in both channels.
Effects loop from the head to dbx input A
Output Channel A of the Dbx to the input of channel B
Output of channel B returning for the effects loop ir the head.
Now using the stereo buttom I can go for the settings of channel 2 (disabled) or channel 1 (enabled).
I hope this helps...