Hi !
In our family there are two Praktica cameras: I personally own a Praktica BX 20 and my mom owns a Praktica BCS.
A few months ago I bought a used BX winder for my camera. After some minor repairing on the contacts it is now working to my full satisfaction with my BX20.
First, here are some pictures of the top and bottom of my BX winder, to support my further explanations:
Pin no. 1 was the easiest to determine:
It seems that this one is only used when the winder is attached to non-BX bodies, since it is in the position of the rewind-release pin (or whatever this is called in English ;-) on the BCS body I have. Also, when opening the housing of the winder, I found that this pin has no real function for the winder itself. I think it is for reaching that rewind-release button on the bottom of the camera body while the winder is attached to it.
Pin no. 3 (weird ordering ;-) also makes sense to me:
It is thicker than the others and seems more stable. Furthermore, the respective hole in the bottom of my BX20 body is really deep and drilled right into the real metal body. This makes me believe that this pin is to hold the winder in its place, to prevent twisting of the winder against the camera body when it is winding, or even reaching the end of the film.
Pin no. 2 is not so easy:
Its default position is "up". So when you attach the winder onto a camera it is supposed to be pushed inwards. But my BX20 body has a hole in its bottom plastic housing where this pin fits into. So it is not depressed when attaching the winder onto it.
Besides that, this pin has some function inside the winder, although I am not quite sure, which function this would be.
So my assumption is, that when attaching this winder onto a non-BX body, this pin would be depressed, somehow adapting the winder to the needs of a non-BX body.
Hopefully this was of any use for you.
And please, drop me a line if you have any further information on this issue.
Christian Staake, Staaki@gmx.net, 2001