The cable reels are for a communication & targetting setup when they are in AA setup.
I found a link, but for some reason cannot post it, will try and sort later.
But they would be linked to other 88's and a communication truck and they would give targets for them and allow communication between all the guns in the battery.
In AT setup, the gun wouldn't be connected like this and most likely setup singly but the gun was that flexible it was great in both roles.
A very advanced set of weaponry for its time!