A possibly-stupid question: why are these things called "location" cabinets?
I have understood them to be "on location" - i.e. near the equipment that they control - rather than being back in the signal box.
You can have lots of wires from the signal (or track circuit, axle counter, etc) back to the location cabinet, but then just one wire [pair] back to the distant signal box, where the signal widens out into a lot of complex wiring. We do rather the same thing in IT, where you have complex server but then that reduces down to a very simple thing connection to what might be a thick application / client. It's why stuff gets compressed into .zips or images into .jpgs which are a lot lighter than one byte / unit of colour per pixel.
Here's a diagram of how this works.
The head on the top represents the
signaller / controller - the unit behind the co-ordination of the whole thing.
That connects via quite a thin connection to a box of tricks in the largely black container. That's the
signal box.
Another thinner section for the wiring out to the
location cabinet, which is the largely hot pink box of tricks on this diagram, and in this example is controlling two
pieces of trackside equipment connected in from below.
Two appendages come out from the signal box. One can be used to
join to the next signal box logic (you can see the connector on the end) and the other is a
roving engineer based at the signal box - his reach is long enough to get into either of the two boxes (the black one and the pink one) and do things there, but special measures have to be taken if he's working trackside at the very bottom of the diagram ...
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