Block Detectors 101

[OBJack]

I have been given an NCE Power Pro block detector to use as a detector for a RR crossing and signal system which I had bought at some "dodgy" stall at a train show a while back.
The old system used light or IR sensors as detectors, but now I need to know what is needed to make this new block detector work.
And to try to get a handle on what the description...."The logic output of the detector is open collector means, which I assume is the basis of all understanding.
So if anyone can tell me slowly enough, and in single syllable words what it all means and what "signal systems logic" is all about I would be forever in their debt.
I have lengths of isolated rail either side of the crossing so I be thinking block detection is the way to go here.

here is a pic of the said block detector


Speak slowly now, so I can follow.

Thanks for your patience.