what are all these buttons? (Squier active V)

[LarryWooten]

Hi, I have questions about my Squier Deluxe Jazz Bass Active V 5-String Electric Bass.
First off, I know that the first button controls the volume but what are the second, third (duplex), and fourth knobs for? Also, what exactly does the "slap switch" do?
I have looked for a schematic on the Fender Squier website and couldn't find one.
This bass incidentally has pickups that are the same size as my four string bass pickups. They are too narrow for my five strings, the low B string is out of range and too quiet as a result. I have to put some soapbars in place of these. Any recommendations? I like the sound it has presently, just the B string is too quiet.
Thanks! Larry

 

[gary m]

The second pot controls balance between the neck and bridge pickup, with the detent being equal level between the two. The stacked pots are low boost/cut and high boost/cut. The last pot controls the midrange boost/cut. The slap switch engages a severe scooping of the midrange frequencies.