Hi want to ask - is it possible to set poe voltage on rb750UP. I want to use 750up to power up ip cam but it is 12V only 
it is not possible to regulate voltage supplied by RB850UP other than using PSU that gives you voltage on the output that you desire. To get 12V on the output on around 30m PoE leads you should have 14V - 15V PSU to power up RB750UP.