Thanks Mel

Quote Originally Posted by Melanie View Post
There's a thousand non-contact ways of doing this...

Why not just have a Barcode on a plate on the back of the Trailer which is scanned from inside the cab?).
This sounds a good idea which means the details of the trailer would on the barcode

An iButton powered by RF tuned circuit or inductive loop
(Not sure about this one i haven't a clue)

There's lots of ways where the target (trailer) can have a device attached which can be powered by the source (cab) without the nescessity of any contact wiring.
I am not quite sure what you mean here could you please expand on this mel

But there's also lots of ways of reading Data from a distance without the target being powered in any shape or form anyway (ie like a Barcode, or Optical Character Recognition etc etc