Interestingly (or not, as the case may be
), being across
something is an old telephone engineer's phrase which goes back many decades. With the road up and a bunch of wires in your hand, you would don your headphones ('cans') with croc clips on the end, apply the croc clips to a pair
(of wires) and listen across
the pair to see if someone's line was working.
These days I believe they call it phone hacking
The TV/Radio industry (my neck of the woods) uses many of the same principles/techniques and indeed equipment to move signals around (within buildings or across the country and beyond). It's a phrase we use a lot at work.
I bet ZF used exactly the same terminology when using field telephones in the Army?