Help with wiring SD blackout B pickup

[JebemMajke]

I know it is not a stompbox but I have a few questions

So my pickup has 5 prongs total on the back.

3 left 2 right.

it says

j1
ground
9v

gain
j2 hot

The guy that previously owned the pickup ( bought used ) shorted j1's wire to the ground and used either j2 hot or gain.

So i am going to use new wires, but i don't know what to do with j1 j2 and gain.

My guess is either j1 or j2 is the output and the other one should be shorted to the ground for Humbucker. But, what to do with gain?

I am planing to use just vol, no tone pot. So i have an extra hole for splitting and/or turning on or off that gain stuff.

What does gain wire do here?

[JebemMajke]

I figured it out, i think.

j1 should be the output, j2 and gain should have a jumper, in order for it to be at full blast. And if they are not connected gain is a bit off and a pickup is cleaner. So it could be used on a switch, as a boost of some sorts, or as a gain lowerer, if it makes sense ...