for example:
i use a DMX Console for 12 dimmer channels. so i connect the output of the 12Channel desk via a female to male adatper to the DMX A input and then?
Do i have to root the DMX A input to the DMX B output? and lose 512 DMX Channels?
When DMX input is activated automatically the last available DMX output to the DMX In. In your case Out B. Now you can say into which universe the DMX In is to be merged. Now in your case the 12 DMX channels from your desk simply merged into the chosen universe.
If you have a chimp 100 then the out B is your DMX IN. As far as I know is always the last output as DMX IN from the desk taken. There is no influence. Read the manual, here it is explained.