units can be coupled to each other. The reason this is not done on all
stock
is because it requires the electrical wiring to be duplicated through
the
coupling (couplers are either left or right handed, IYSWIM), which is
more
expensive and more prone to failure.

I've no idea how its actually done but couldn't they just be connected
with
seperate cables (instead of via the coupler), which twist in the middle
so
to match up with the other unit?

eg:

A --- ----B
\ /
\ /
/ \
/ \
B--- ----A

B2003