Thanks for the links John but they are mostly stuff I found before - basically makers sales sheets and pictures. These presuppose I know what to do with a waterfall winch :)
However I get the impression that one way or another these are all two functional winches, not a winch with a spare reel. I've seen something about the Aziz winch being a winch plus spare cable but I wonder if that is a myth started by someone who assumed that and which has become 'fact' through repetition.
The second winch on the Aziz
would be a spare cable. BUT, it is also a working winch, not just a spool of cable.
If you are towing at sea, and the towing cable parts, you can't just leave the tow, and go back to port for a new cable.
The second winch, will allow the boat to run a new line to the tow, and continue on its way. (there by using it's spare cable to continue its work.)
The waterfall configuration saves space, instead of a winches two wide on the deck, they waterfall winch can be
installed on narrower profiles. Also, if an existing boat wanted to install a second winch, the waterfall style winch can
be retrofitted into the existing space with out losing as much deck space as installing an entire second winch.